diff --git a/doc/api/http.md b/doc/api/http.md
index 77dd231ebb6fef..32752562fa2b0f 100644
--- a/doc/api/http.md
+++ b/doc/api/http.md
@@ -4361,6 +4361,31 @@ added:
 
 Set the maximum number of idle HTTP parsers.
 
+## `http.setGlobalProxyFromEnv(proxyEnv)`
+
+<!-- YAML
+added:
+  - REPLACEME
+-->
+
+* `proxyEnv` {Object} An object containing proxy configuration. This accepts the
+  same options as the `proxyEnv` option accepted by [`Agent`][]
+* Returns: {Function} A function that restores the original agent and dispatcher
+  settings to the state before this `http.setGlobalProxyFromEnv()` is invoked.
+
+Dynamically resets the global configurations to enable built-in proxy support for
+`fetch()` and `http.request()`/`https.request()` at runtime, as an alternative
+to using the `--use-env-proxy` flag or `NODE_USE_ENV_PROXY` environment variable.
+It can also be used to override settings configured from the environment variables.
+
+As this function resets the global configurations, any previously configured
+`http.globalAgent`, `https.globalAgent` or undici global dispatcher would be
+overridden after this function is invoked. It's recommended to invoke it before any
+requests are made and avoid invoking it in the middle of any requests.
+
+See [Built-in Proxy Support][] for details on proxy URL formats and `NO_PROXY`
+syntax.
+
 ## Class: `WebSocket`
 
 <!-- YAML
@@ -4383,6 +4408,9 @@ added:
 When Node.js creates the global agent, if the `NODE_USE_ENV_PROXY` environment variable is
 set to `1` or `--use-env-proxy` is enabled, the global agent will be constructed
 with `proxyEnv: process.env`, enabling proxy support based on the environment variables.
+
+To enable proxy support dynamically and globally, use [`http.setGlobalProxyFromEnv()`][].
+
 Custom agents can also be created with proxy support by passing a
 `proxyEnv` option when constructing the agent. The value can be `process.env`
 if they just want to inherit the configuration from the environment variables,
@@ -4438,6 +4466,65 @@ Or the `--use-env-proxy` flag.
 HTTP_PROXY=http://proxy.example.com:8080 NO_PROXY=localhost,127.0.0.1 node --use-env-proxy client.js
 ```
 
+To enable proxy support dynamically and globally:
+
+```cjs
+const http = require('node:http');
+
+const restore = http.setGlobalProxyFromEnv({
+  http_proxy: 'http://proxy.example.com:8080',
+  https_proxy: 'https://proxy.example.com:8443',
+  no_proxy: 'localhost,127.0.0.1,.internal.example.com',
+});
+
+// Subsequent requests will use the configured proxies
+http.get('http://www.example.com', (res) => {
+  // This request will be proxied through proxy.example.com:8080
+});
+
+fetch('https://www.example.com', (res) => {
+  // This request will be proxied through proxy.example.com:8443
+});
+```
+
+```mjs
+import http from 'node:http';
+
+http.setGlobalProxyFromEnv({
+  http_proxy: 'http://proxy.example.com:8080',
+  https_proxy: 'https://proxy.example.com:8443',
+  no_proxy: 'localhost,127.0.0.1,.internal.example.com',
+});
+
+// Subsequent requests will use the configured proxies
+http.get('http://www.example.com', (res) => {
+  // This request will be proxied through proxy.example.com:8080
+});
+
+fetch('https://www.example.com', (res) => {
+  // This request will be proxied through proxy.example.com:8443
+});
+```
+
+To clear the dynamically enabled global proxy configuration:
+
+```cjs
+const http = require('node:http');
+const restore = http.setGlobalProxyFromEnv({ /* ... */ });
+// Perform requests that will be proxied.
+restore();
+// From now on, requests will no longer be proxied.
+```
+
+```mjs
+import http from 'node:http';
+
+const restore = http.setGlobalProxyFromEnv({ /* ... */ });
+// Perform requests that will be proxied.
+restore();
+// From now on, requests will no longer be proxied.
+```
+
 To create a custom agent with built-in proxy support:
 
 ```cjs
@@ -4501,6 +4588,7 @@ const agent2 = new http.Agent({ proxyEnv: process.env });
 [`http.get()`]: #httpgetoptions-callback
 [`http.globalAgent`]: #httpglobalagent
 [`http.request()`]: #httprequestoptions-callback
+[`http.setGlobalProxyFromEnv()`]: #httpsetglobalproxyfromenvproxyenv
 [`message.headers`]: #messageheaders
 [`message.rawHeaders`]: #messagerawheaders
 [`message.socket`]: #messagesocket
diff --git a/lib/_http_agent.js b/lib/_http_agent.js
index c936bc16228d33..ea5d44306f09e5 100644
--- a/lib/_http_agent.js
+++ b/lib/_http_agent.js
@@ -40,7 +40,7 @@ const {
   kProxyConfig,
   checkShouldUseProxy,
   kWaitForProxyTunnel,
-  filterEnvForProxies,
+  getGlobalAgent,
 } = require('internal/http');
 const { AsyncResource } = require('async_hooks');
 const { async_id_symbol } = require('internal/async_hooks').symbols;
@@ -627,9 +627,5 @@ function asyncResetHandle(socket) {
 
 module.exports = {
   Agent,
-  globalAgent: new Agent({
-    keepAlive: true, scheduling: 'lifo', timeout: 5000,
-    // This normalized from both --use-env-proxy and NODE_USE_ENV_PROXY settings.
-    proxyEnv: getOptionValue('--use-env-proxy') ? filterEnvForProxies(process.env) : undefined,
-  }),
+  globalAgent: getGlobalAgent(getOptionValue('--use-env-proxy') ? process.env : undefined, Agent),
 };
diff --git a/lib/http.js b/lib/http.js
index 96ea32cf1b1034..72b2b5af8d598f 100644
--- a/lib/http.js
+++ b/lib/http.js
@@ -30,6 +30,7 @@ const httpAgent = require('_http_agent');
 const { ClientRequest } = require('_http_client');
 const { methods, parsers } = require('_http_common');
 const { IncomingMessage } = require('_http_incoming');
+const { ERR_PROXY_INVALID_CONFIG } = require('internal/errors').codes;
 const {
   validateHeaderName,
   validateHeaderValue,
@@ -41,6 +42,11 @@ const {
   Server,
   ServerResponse,
 } = require('_http_server');
+const {
+  parseProxyUrl,
+  getGlobalAgent,
+} = require('internal/http');
+const { URL } = require('internal/url');
 let maxHeaderSize;
 let undici;
 
@@ -123,6 +129,57 @@ function lazyUndici() {
   return undici ??= require('internal/deps/undici/undici');
 }
 
+function setGlobalProxyFromEnv(env) {
+  const httpProxy = parseProxyUrl(env, 'http:');
+  const httpsProxy = parseProxyUrl(env, 'https:');
+  const noProxy = env.no_proxy || env.NO_PROXY;
+
+  if (!httpProxy && !httpsProxy) {
+    return () => {};
+  }
+
+  if (httpProxy && !URL.canParse(httpProxy)) {
+    throw new ERR_PROXY_INVALID_CONFIG(httpProxy);
+  }
+  if (httpsProxy && !URL.canParse(httpsProxy)) {
+    throw new ERR_PROXY_INVALID_CONFIG(httpsProxy);
+  }
+
+  let originalDispatcher, originalHttpsAgent, originalHttpAgent;
+  if (httpProxy || httpsProxy) {
+    // Set it for fetch.
+    const { setGlobalDispatcher, getGlobalDispatcher, EnvHttpProxyAgent } = lazyUndici();
+    const envHttpProxyAgent = new EnvHttpProxyAgent({
+      __proto__: null, httpProxy, httpsProxy, noProxy,
+    });
+    originalDispatcher = getGlobalDispatcher();
+    setGlobalDispatcher(envHttpProxyAgent);
+  }
+
+  if (httpProxy) {
+    originalHttpAgent = module.exports.globalAgent;
+    module.exports.globalAgent = getGlobalAgent(env, httpAgent.Agent);
+  }
+  if (httpsProxy && !!process.versions.openssl) {
+    const https = require('https');
+    originalHttpsAgent = https.globalAgent;
+    https.globalAgent = getGlobalAgent(env, https.Agent);
+  }
+
+  return function restore() {
+    if (originalDispatcher) {
+      const { setGlobalDispatcher } = lazyUndici();
+      setGlobalDispatcher(originalDispatcher);
+    }
+    if (originalHttpAgent) {
+      module.exports.globalAgent = originalHttpAgent;
+    }
+    if (originalHttpsAgent) {
+      require('https').globalAgent = originalHttpsAgent;
+    }
+  };
+}
+
 module.exports = {
   _connectionListener,
   METHODS: methods.toSorted(),
@@ -142,6 +199,7 @@ module.exports = {
     validateInteger(max, 'max', 1);
     parsers.max = max;
   },
+  setGlobalProxyFromEnv,
 };
 
 ObjectDefineProperty(module.exports, 'maxHeaderSize', {
diff --git a/lib/https.js b/lib/https.js
index 799a8f197c7347..1e86e81cf76b15 100644
--- a/lib/https.js
+++ b/lib/https.js
@@ -50,8 +50,8 @@ const tls = require('tls');
 const {
   kProxyConfig,
   checkShouldUseProxy,
-  filterEnvForProxies,
   kWaitForProxyTunnel,
+  getGlobalAgent,
 } = require('internal/http');
 const { Agent: HttpAgent } = require('_http_agent');
 const {
@@ -602,11 +602,7 @@ Agent.prototype._evictSession = function _evictSession(key) {
   delete this._sessionCache.map[key];
 };
 
-const globalAgent = new Agent({
-  keepAlive: true, scheduling: 'lifo', timeout: 5000,
-  // This normalized from both --use-env-proxy and NODE_USE_ENV_PROXY settings.
-  proxyEnv: getOptionValue('--use-env-proxy') ? filterEnvForProxies(process.env) : undefined,
-});
+const globalAgent = getGlobalAgent(getOptionValue('--use-env-proxy') ? process.env : undefined, Agent);
 
 /**
  * Makes a request to a secure web server.
diff --git a/lib/internal/http.js b/lib/internal/http.js
index e664663348adc7..f8b4fd7c4ca5a0 100644
--- a/lib/internal/http.js
+++ b/lib/internal/http.js
@@ -186,11 +186,7 @@ class ProxyConfig {
   }
 }
 
-function parseProxyConfigFromEnv(env, protocol, keepAlive) {
-  // We only support proxying for HTTP and HTTPS requests.
-  if (protocol !== 'http:' && protocol !== 'https:') {
-    return null;
-  }
+function parseProxyUrl(env, protocol) {
   // Get the proxy url - following the most popular convention, lower case takes precedence.
   // See https://about.gitlab.com/blog/we-need-to-talk-no-proxy/#http_proxy-and-https_proxy
   const proxyUrl = (protocol === 'https:') ?
@@ -204,6 +200,20 @@ function parseProxyConfigFromEnv(env, protocol, keepAlive) {
     throw new ERR_PROXY_INVALID_CONFIG(`Invalid proxy URL: ${proxyUrl}`);
   }
 
+  return proxyUrl;
+}
+
+function parseProxyConfigFromEnv(env, protocol, keepAlive) {
+  // We only support proxying for HTTP and HTTPS requests.
+  if (protocol !== 'http:' && protocol !== 'https:') {
+    return null;
+  }
+
+  const proxyUrl = parseProxyUrl(env, protocol);
+  if (proxyUrl === null) {
+    return null;
+  }
+
   // Only http:// and https:// proxies are supported.
   // Ignore instead of throw, in case other protocols are supposed to be
   // handled by the user land.
@@ -244,6 +254,13 @@ function filterEnvForProxies(env) {
   };
 }
 
+function getGlobalAgent(proxyEnv, Agent) {
+  return new Agent({
+    keepAlive: true, scheduling: 'lifo', timeout: 5000,
+    proxyEnv,
+  });
+}
+
 module.exports = {
   kOutHeaders: Symbol('kOutHeaders'),
   kNeedDrain: Symbol('kNeedDrain'),
@@ -257,4 +274,6 @@ module.exports = {
   getNextTraceEventId,
   isTraceHTTPEnabled,
   filterEnvForProxies,
+  getGlobalAgent,
+  parseProxyUrl,
 };
diff --git a/test/client-proxy/test-http-proxy-fetch.mjs b/test/client-proxy/test-http-proxy-fetch.mjs
index 493ff022e1aa74..81118fe9ead827 100644
--- a/test/client-proxy/test-http-proxy-fetch.mjs
+++ b/test/client-proxy/test-http-proxy-fetch.mjs
@@ -20,9 +20,7 @@ await once(proxy, 'listening');
 const serverHost = `localhost:${server.address().port}`;
 
 // FIXME(undici:4083): undici currently always tunnels the request over
-// CONNECT if proxyTunnel is not explicitly set to false, but what we
-// need is for it to be automatically false for HTTP requests to be
-// consistent with curl.
+// CONNECT if proxyTunnel is not explicitly set to false.
 const expectedLogs = [{
   method: 'CONNECT',
   url: serverHost,
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-fetch-empty.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-fetch-empty.mjs
new file mode 100644
index 00000000000000..a4c6cc5f52fbeb
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-fetch-empty.mjs
@@ -0,0 +1,21 @@
+// Tests that http.setGlobalProxyFromEnv() is a no-op when no proxy is configured.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { startTestServers, checkProxiedFetch } from '../common/proxy-server.js';
+
+const { proxyLogs, shutdown, httpEndpoint: { requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+
+await checkProxiedFetch({
+  FETCH_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({}),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+
+// Verify request did NOT go through proxy.
+assert.deepStrictEqual(proxyLogs, []);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-fetch-https.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-fetch-https.mjs
new file mode 100644
index 00000000000000..d685d8fe5f9076
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-fetch-https.mjs
@@ -0,0 +1,38 @@
+// Tests that http.setGlobalProxyFromEnv() works with fetch().
+
+import * as common from '../common/index.mjs';
+import assert from 'node:assert';
+import * as fixtures from '../common/fixtures.mjs';
+import { startTestServers, checkProxiedFetch } from '../common/proxy-server.js';
+
+if (!common.hasCrypto) {
+  common.skip('Needs crypto');
+}
+
+const { proxyLogs, proxyUrl, shutdown, httpsEndpoint: { serverHost, requestUrl } } = await startTestServers({
+  httpsEndpoint: true,
+});
+
+await checkProxiedFetch({
+  FETCH_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    https_proxy: proxyUrl,
+  }),
+  NODE_EXTRA_CA_CERTS: fixtures.path('keys', 'fake-startcom-root-cert.pem'),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+
+const expectedLogs = [{
+  method: 'CONNECT',
+  url: serverHost,
+  headers: {
+    'connection': 'close',
+    'host': serverHost,
+    'proxy-connection': 'keep-alive',
+  },
+}];
+
+assert.deepStrictEqual(proxyLogs, expectedLogs);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-fetch-no-proxy.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-fetch-no-proxy.mjs
new file mode 100644
index 00000000000000..30f53add60fd51
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-fetch-no-proxy.mjs
@@ -0,0 +1,23 @@
+// Tests that http.setGlobalProxyFromEnv() works with no_proxy configuration.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { startTestServers, checkProxiedFetch } from '../common/proxy-server.js';
+const { proxyLogs, shutdown, proxyUrl, httpEndpoint: { requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+
+await checkProxiedFetch({
+  FETCH_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    http_proxy: proxyUrl,
+    no_proxy: 'localhost',
+  }),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+
+// Verify request did NOT go through proxy.
+assert.deepStrictEqual(proxyLogs, []);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-fetch-restore.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-fetch-restore.mjs
new file mode 100644
index 00000000000000..c68ac863abe3e7
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-fetch-restore.mjs
@@ -0,0 +1,35 @@
+// Tests that http.setGlobalProxyFromEnv() works with fetch() and https.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { startTestServers, checkProxiedFetch } from '../common/proxy-server.js';
+
+const { proxyLogs, proxyUrl, shutdown, httpEndpoint: { serverHost, requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+
+await checkProxiedFetch({
+  FETCH_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    http_proxy: proxyUrl,
+  }),
+  CLEAR_GLOBAL_PROXY_AND_RETRY: '1',
+}, {
+  stdout: 'Hello world\nHello world',
+});
+
+shutdown();
+
+// FIXME(undici:4083): undici currently always tunnels the request over
+// CONNECT if proxyTunnel is not explicitly set to false.
+const expectedLogs = [{
+  method: 'CONNECT',
+  url: serverHost,
+  headers: {
+    'connection': 'close',
+    'host': serverHost,
+    'proxy-connection': 'keep-alive',
+  },
+}];
+
+assert.deepStrictEqual(proxyLogs, expectedLogs);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-fetch.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-fetch.mjs
new file mode 100644
index 00000000000000..accfbc1e54de25
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-fetch.mjs
@@ -0,0 +1,34 @@
+// Tests that http.setGlobalProxyFromEnv() works with fetch() and https.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { startTestServers, checkProxiedFetch } from '../common/proxy-server.js';
+
+const { proxyLogs, proxyUrl, shutdown, httpEndpoint: { serverHost, requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+
+await checkProxiedFetch({
+  FETCH_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    http_proxy: proxyUrl,
+  }),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+
+// FIXME(undici:4083): undici currently always tunnels the request over
+// CONNECT if proxyTunnel is not explicitly set to false.
+const expectedLogs = [{
+  method: 'CONNECT',
+  url: serverHost,
+  headers: {
+    'connection': 'close',
+    'host': serverHost,
+    'proxy-connection': 'keep-alive',
+  },
+}];
+
+assert.deepStrictEqual(proxyLogs, expectedLogs);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-http-request-empty.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-http-request-empty.mjs
new file mode 100644
index 00000000000000..9c1d0a9575b121
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-http-request-empty.mjs
@@ -0,0 +1,20 @@
+// Tests that http.setGlobalProxyFromEnv() is a no-op when no proxy is configured.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { startTestServers, checkProxiedRequest } from '../common/proxy-server.js';
+const { proxyLogs, shutdown, httpEndpoint: { requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+
+await checkProxiedRequest({
+  REQUEST_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({}),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+
+// Verify request did NOT go through proxy.
+assert.deepStrictEqual(proxyLogs, []);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-http-request-restore.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-http-request-restore.mjs
new file mode 100644
index 00000000000000..bede1041199720
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-http-request-restore.mjs
@@ -0,0 +1,33 @@
+// Tests that http.setGlobalProxyFromEnv() works with fetch() and https.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { startTestServers, checkProxiedRequest } from '../common/proxy-server.js';
+
+const { proxyLogs, proxyUrl, shutdown, httpEndpoint: { serverHost, requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+
+await checkProxiedRequest({
+  REQUEST_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    http_proxy: proxyUrl,
+  }),
+  CLEAR_GLOBAL_PROXY_AND_RETRY: '1',
+}, {
+  stdout: 'Hello worldHello world',
+});
+
+shutdown();
+
+const expectedLogs = [{
+  method: 'GET',
+  url: requestUrl,
+  headers: {
+    'connection': 'keep-alive',
+    'proxy-connection': 'keep-alive',
+    'host': serverHost,
+  },
+}];
+
+assert.deepStrictEqual(proxyLogs, expectedLogs);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-http-request.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-http-request.mjs
new file mode 100644
index 00000000000000..0e834bbc2d440d
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-http-request.mjs
@@ -0,0 +1,29 @@
+// Tests that http.setGlobalProxyFromEnv() works with http.request().
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { startTestServers, checkProxiedRequest } from '../common/proxy-server.js';
+const { proxyLogs, shutdown, proxyUrl, httpEndpoint: { requestUrl, serverHost } } = await startTestServers({
+  httpEndpoint: true,
+});
+
+await checkProxiedRequest({
+  REQUEST_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({ http_proxy: proxyUrl }),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+
+const expectedLogs = [{
+  method: 'GET',
+  url: requestUrl,
+  headers: {
+    'connection': 'keep-alive',
+    'proxy-connection': 'keep-alive',
+    'host': serverHost,
+  },
+}];
+
+assert.deepStrictEqual(proxyLogs, expectedLogs);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-https-request.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-https-request.mjs
new file mode 100644
index 00000000000000..65b67dd48c68f3
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-https-request.mjs
@@ -0,0 +1,37 @@
+// Tests that http.setGlobalProxyFromEnv() works with https.request().
+
+import * as common from '../common/index.mjs';
+import assert from 'node:assert';
+import * as fixtures from '../common/fixtures.mjs';
+import { startTestServers, checkProxiedRequest } from '../common/proxy-server.js';
+
+if (!common.hasCrypto) {
+  common.skip('Needs crypto');
+}
+
+const { proxyLogs, httpsEndpoint: { requestUrl, serverHost }, proxyUrl, shutdown } = await startTestServers({
+  httpsEndpoint: true,
+});
+
+await checkProxiedRequest({
+  REQUEST_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    https_proxy: proxyUrl,
+  }),
+  NODE_EXTRA_CA_CERTS: fixtures.path('keys', 'fake-startcom-root-cert.pem'),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+
+const expectedLogs = [{
+  method: 'CONNECT',
+  url: serverHost,
+  headers: {
+    'proxy-connection': 'keep-alive',
+    'host': serverHost,
+  },
+}];
+
+assert.deepStrictEqual(proxyLogs, expectedLogs);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-invalid-url.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-invalid-url.mjs
new file mode 100644
index 00000000000000..8095043ca6f03d
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-invalid-url.mjs
@@ -0,0 +1,21 @@
+// Tests that http.setGlobalProxyFromEnv() throws on invalid HTTP proxy URL.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import http from 'node:http';
+
+assert.throws(() => {
+  http.setGlobalProxyFromEnv({
+    http_proxy: 'not a url',
+  });
+}, {
+  code: 'ERR_PROXY_INVALID_CONFIG',
+});
+
+assert.throws(() => {
+  http.setGlobalProxyFromEnv({
+    https_proxy: 'not a url',
+  });
+}, {
+  code: 'ERR_PROXY_INVALID_CONFIG',
+});
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-no-proxy.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-no-proxy.mjs
new file mode 100644
index 00000000000000..fa3568fff71102
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-no-proxy.mjs
@@ -0,0 +1,23 @@
+// Tests that http.setGlobalProxyFromEnv() works with no_proxy configuration.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { startTestServers, checkProxiedRequest } from '../common/proxy-server.js';
+const { proxyLogs, shutdown, proxyUrl, httpEndpoint: { requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+
+await checkProxiedRequest({
+  REQUEST_URL: requestUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    http_proxy: proxyUrl,
+    no_proxy: 'localhost',
+  }),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+
+// Verify request did NOT go through proxy.
+assert.deepStrictEqual(proxyLogs, []);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-override-fetch.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-override-fetch.mjs
new file mode 100644
index 00000000000000..04bcbc33c50eda
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-override-fetch.mjs
@@ -0,0 +1,44 @@
+// Tests that http.setGlobalProxyFromEnv() overrides configuration from NODE_USE_ENV_PROXY.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { once } from 'node:events';
+import { startTestServers, checkProxiedFetch, createProxyServer } from '../common/proxy-server.js';
+const { proxyLogs, shutdown, proxyUrl, httpEndpoint: { serverHost, requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+const { proxy: proxy2, logs: proxyLogs2 } = createProxyServer();
+proxy2.listen(0);
+await once(proxy2, 'listening');
+
+await checkProxiedFetch({
+  FETCH_URL: requestUrl,
+  NODE_USE_ENV_PROXY: '1',
+  http_proxy: proxyUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    http_proxy: `http://localhost:${proxy2.address().port}`,
+  }),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+proxy2.close();
+
+// Verify request did NOT go through original proxy, but the overriden one.
+assert.deepStrictEqual(proxyLogs, []);
+
+// FIXME(undici:4083): undici currently always tunnels the request over
+// CONNECT if proxyTunnel is not explicitly set to false, but what we
+// need is for it to be automatically false for HTTP requests to be
+// consistent with curl.
+const expectedLogs = [{
+  method: 'CONNECT',
+  url: serverHost,
+  headers: {
+    'connection': 'close',
+    'host': serverHost,
+    'proxy-connection': 'keep-alive',
+  },
+}];
+assert.deepStrictEqual(proxyLogs2, expectedLogs);
diff --git a/test/client-proxy/test-http-set-global-proxy-from-env-override-http.mjs b/test/client-proxy/test-http-set-global-proxy-from-env-override-http.mjs
new file mode 100644
index 00000000000000..a09d29831b58c6
--- /dev/null
+++ b/test/client-proxy/test-http-set-global-proxy-from-env-override-http.mjs
@@ -0,0 +1,40 @@
+// Tests that http.setGlobalProxyFromEnv() overrides configuration from NODE_USE_ENV_PROXY.
+
+import '../common/index.mjs';
+import assert from 'node:assert';
+import { once } from 'node:events';
+import { startTestServers, checkProxiedRequest, createProxyServer } from '../common/proxy-server.js';
+const { proxyLogs, shutdown, proxyUrl, httpEndpoint: { serverHost, requestUrl } } = await startTestServers({
+  httpEndpoint: true,
+});
+const { proxy: proxy2, logs: proxyLogs2 } = createProxyServer();
+proxy2.listen(0);
+await once(proxy2, 'listening');
+
+await checkProxiedRequest({
+  REQUEST_URL: requestUrl,
+  NODE_USE_ENV_PROXY: '1',
+  http_proxy: proxyUrl,
+  SET_GLOBAL_PROXY: JSON.stringify({
+    http_proxy: `http://localhost:${proxy2.address().port}`,
+  }),
+}, {
+  stdout: 'Hello world',
+});
+
+shutdown();
+proxy2.close();
+
+// Verify request did NOT go through original proxy, but the overriden one.
+assert.deepStrictEqual(proxyLogs, []);
+
+const expectedLogs = [{
+  method: 'GET',
+  url: requestUrl,
+  headers: {
+    'connection': 'keep-alive',
+    'host': serverHost,
+    'proxy-connection': 'keep-alive',
+  },
+}];
+assert.deepStrictEqual(proxyLogs2, expectedLogs);
diff --git a/test/common/proxy-server.js b/test/common/proxy-server.js
index 7f3ea67b8bbc99..c4cd19fe610b81 100644
--- a/test/common/proxy-server.js
+++ b/test/common/proxy-server.js
@@ -3,6 +3,8 @@
 const net = require('net');
 const http = require('http');
 const assert = require('assert');
+const { once } = require('events');
+const fixtures = require('./fixtures');
 
 function logRequest(logs, req) {
   logs.push({
@@ -14,7 +16,7 @@ function logRequest(logs, req) {
 
 // This creates a minimal proxy server that logs the requests it gets
 // to an array before performing proxying.
-exports.createProxyServer = function(options = {}) {
+function createProxyServer(options = {}) {
   const logs = [];
 
   let proxy;
@@ -107,7 +109,8 @@ exports.createProxyServer = function(options = {}) {
   });
 
   return { proxy, logs };
-};
+}
+exports.createProxyServer = createProxyServer;
 
 function spawnPromisified(...args) {
   const { spawn } = require('child_process');
@@ -148,12 +151,13 @@ function spawnPromisified(...args) {
   });
 }
 
-exports.checkProxiedFetch = async function(envExtension, expectation, cliArgsExtension = []) {
-  const fixtures = require('./fixtures');
+async function checkProxied(type, envExtension, expectation, cliArgsExtension = []) {
+  const script = type === 'fetch' ? fixtures.path('fetch-and-log.mjs') : fixtures.path('request-and-log.js');
   const { code, signal, stdout, stderr } = await spawnPromisified(
     process.execPath,
-    [...cliArgsExtension, fixtures.path('fetch-and-log.mjs')], {
+    [...cliArgsExtension, script], {
       env: {
+        NO_LOG_REQUEST: '1',
         ...process.env,
         ...envExtension,
       },
@@ -172,6 +176,14 @@ exports.checkProxiedFetch = async function(envExtension, expectation, cliArgsExt
   });
 };
 
+exports.checkProxiedFetch = async function(...args) {
+  return checkProxied('fetch', ...args);
+};
+
+exports.checkProxiedRequest = async function(...args) {
+  return checkProxied('request', ...args);
+};
+
 exports.runProxiedRequest = async function(envExtension, cliArgsExtension = []) {
   const fixtures = require('./fixtures');
   return spawnPromisified(
@@ -195,3 +207,55 @@ exports.runProxiedPOST = async function(envExtension) {
       },
     });
 };
+
+exports.startTestServers = async function(options = {}) {
+  const { proxy, logs } = createProxyServer();
+  proxy.listen(0);
+  await once(proxy, 'listening');
+
+  let httpServer, httpsServer, httpEndpoint, httpsEndpoint;
+  if (options.httpsEndpoint) {
+    httpsServer = require('https').createServer({
+      cert: fixtures.readKey('agent8-cert.pem'),
+      key: fixtures.readKey('agent8-key.pem'),
+    }, (req, res) => {
+      res.end('Hello world');
+    });
+    httpsServer.listen(0);
+    await once(httpsServer, 'listening');
+    const { port } = httpsServer.address();
+    httpsEndpoint = {
+      serverHost: `localhost:${port}`,
+      requestUrl: `https://localhost:${port}/test`,
+    };
+  }
+
+  if (options.httpEndpoint) {
+    httpServer = http.createServer((req, res) => {
+      res.end('Hello world');
+    });
+    httpServer.listen(0);
+    await once(httpServer, 'listening');
+    const { port } = httpServer.address();
+    httpEndpoint = {
+      serverHost: `localhost:${port}`,
+      requestUrl: `http://localhost:${port}/test`,
+    };
+  }
+
+  return {
+    proxyLogs: logs,
+    shutdown() {
+      if (httpServer) {
+        httpServer.close();
+      }
+      if (httpsServer) {
+        httpsServer.close();
+      }
+      proxy.close();
+    },
+    proxyUrl: `http://localhost:${proxy.address().port}`,
+    httpEndpoint,
+    httpsEndpoint,
+  };
+};
diff --git a/test/fixtures/fetch-and-log.mjs b/test/fixtures/fetch-and-log.mjs
index d019d29aa2933d..73f24542571ab3 100644
--- a/test/fixtures/fetch-and-log.mjs
+++ b/test/fixtures/fetch-and-log.mjs
@@ -1,3 +1,18 @@
+import http from 'node:http';
+
+let restore;
+if (process.env.SET_GLOBAL_PROXY) {
+  const config = JSON.parse(process.env.SET_GLOBAL_PROXY);
+  restore = http.setGlobalProxyFromEnv(config);
+}
+
 const response = await fetch(process.env.FETCH_URL);
 const body = await response.text();
 console.log(body);
+
+if (process.env.CLEAR_GLOBAL_PROXY_AND_RETRY) {
+  restore();
+  const response = await fetch(process.env.FETCH_URL);
+  const body = await response.text();
+  console.log(body);
+}
diff --git a/test/fixtures/request-and-log.js b/test/fixtures/request-and-log.js
index 77291e78e3bfa6..80de5b56c409e1 100644
--- a/test/fixtures/request-and-log.js
+++ b/test/fixtures/request-and-log.js
@@ -1,3 +1,9 @@
+let restore;
+if (process.env.SET_GLOBAL_PROXY) {
+  const config = JSON.parse(process.env.SET_GLOBAL_PROXY);
+  restore = require('http').setGlobalProxyFromEnv(config);
+}
+
 const url = process.env.REQUEST_URL;
 
 let lib;
@@ -32,24 +38,39 @@ if (process.env.RESOLVE_TO_LOCALHOST) {
   };
 }
 
-const req = request(url, {
-  timeout,
-  agent,
-  lookup,
-}, (res) => {
-  // Log the status code
-  console.log(`Status Code: ${res.statusCode}`);
-  console.log('Headers:', res.headers);
-  res.pipe(process.stdout);
-});
+function startRequest(callback) {
+  const req = request(url, {
+    timeout,
+    agent,
+    lookup,
+  }, (res) => {
+    // Log the status code
+    if (!process.env.NO_LOG_REQUEST) {
+      console.log(`Status Code: ${res.statusCode}`);
+      console.log('Headers:', res.headers);
+    }
+    res.pipe(process.stdout);
 
-req.on('error', (e) => {
-  console.error('Request Error', e);
-});
+    if (callback) {
+      res.on('end', callback);
+    }
+  });
 
-req.on('timeout', () => {
-  console.error('Request timed out');
-  req.destroy();
-});
+  req.on('error', (e) => {
+    console.error('Request Error', e);
+  });
+
+  req.on('timeout', () => {
+    console.error('Request timed out');
+    req.destroy();
+  });
 
-req.end();
+  req.end();
+}
+
+startRequest(() => {
+  if (process.env.CLEAR_GLOBAL_PROXY_AND_RETRY) {
+    restore();
+    startRequest();
+  }
+});