diff --git a/build/tasks/test-on-node.js b/build/tasks/test-on-node.js
index 5f87be5aa..05bef4427 100644
--- a/build/tasks/test-on-node.js
+++ b/build/tasks/test-on-node.js
@@ -16,8 +16,9 @@ module.exports = function (grunt) {
       grunt.log.ok(`Ran ${totals.files} files`);
     }
 
-    // Refresh the QUnit global to be used in other tests
-    global.QUnit = requireFresh('../../qunit/qunit.js');
+    // Reset for anything after this task
+    delete globalThis.QUnit;
+    delete require.cache[require.resolve('../../qunit/qunit.js')];
 
     done(!totals.failed);
   });
@@ -31,11 +32,9 @@ module.exports = function (grunt) {
   function runQUnit (file, runEnd) {
     // Resolve current QUnit path and remove it from the require cache
     // to avoid stacking the QUnit logs.
+    delete globalThis.QUnit;
     let QUnit = requireFresh('../../qunit/qunit.js');
 
-    // Expose QUnit to the global scope to be seen on the other tests.
-    global.QUnit = QUnit;
-
     QUnit.config.autostart = false;
     requireFresh('../../' + file);
     registerEvents(QUnit, file, runEnd);
diff --git a/src/cli/run.js b/src/cli/run.js
index fe3aad4d2..89f70681c 100644
--- a/src/cli/run.js
+++ b/src/cli/run.js
@@ -64,10 +64,6 @@ async function run (args, options) {
     console.log(`Running tests with seed: ${QUnit.config.seed}`);
   }
 
-  // TODO: Enable mode where QUnit is not auto-injected, but other setup is
-  // still done automatically.
-  global.QUnit = QUnit;
-
   options.requires.forEach(requireFromCWD);
 
   findReporter(options.reporter, QUnit.reporters).init(QUnit);
@@ -176,7 +172,7 @@ function abort (callback) {
     process.off('exit', onExit);
     running = false;
 
-    delete global.QUnit;
+    delete globalThis.QUnit;
     QUnit = null;
     if (callback) {
       callback();
@@ -196,8 +192,7 @@ run.watch = function watch (args, options) {
   const watch = require('node-watch');
   const baseDir = process.cwd();
 
-  QUnit = requireQUnit();
-  global.QUnit = QUnit;
+  requireQUnit();
   options.requires.forEach(requireFromCWD);
 
   // Include TypeScript when in use (automatically via require.extensions),
diff --git a/src/core.js b/src/core.js
index fa083fc57..c12230f63 100644
--- a/src/core.js
+++ b/src/core.js
@@ -5,7 +5,6 @@ import dump from './dump';
 import { runSuite, module } from './module';
 import Assert from './assert';
 import Test, { test, pushFailure } from './test';
-import exportQUnit from './export';
 import reporters from './reporters';
 
 import config from './core/config';
@@ -141,6 +140,4 @@ function begin () {
   }).then(unblockAndAdvanceQueue);
 }
 
-exportQUnit(QUnit);
-
 export default QUnit;
diff --git a/src/core/config.js b/src/core/config.js
index 86e07bb91..d63835dbe 100644
--- a/src/core/config.js
+++ b/src/core/config.js
@@ -212,7 +212,7 @@ readFlatPreconfig(globalThis);
 // Apply a predefined QUnit.config object
 //
 // Ignore QUnit.config if it is a QUnit distribution instead of preconfig.
-// That means QUnit was loaded twice! (Use the same approach as export.js)
+// This should use the same heuristic as the export in qunit.js.
 const preConfig = globalThis && globalThis.QUnit && !globalThis.QUnit.version && globalThis.QUnit.config;
 if (preConfig) {
   extend(config, preConfig);
diff --git a/src/export.js b/src/export.js
deleted file mode 100644
index cbf15b3c3..000000000
--- a/src/export.js
+++ /dev/null
@@ -1,40 +0,0 @@
-/* global module, exports */
-import { window, document, globalThis } from './globals';
-
-export default function exportQUnit (QUnit) {
-  let exportedModule = false;
-
-  if (window && document) {
-    // QUnit may be defined when it is preconfigured but then only QUnit and QUnit.config may be defined.
-    if (window.QUnit && window.QUnit.version) {
-      throw new Error('QUnit has already been defined.');
-    }
-
-    window.QUnit = QUnit;
-
-    exportedModule = true;
-  }
-
-  // For Node.js
-  if (typeof module !== 'undefined' && module && module.exports) {
-    module.exports = QUnit;
-
-    // For consistency with CommonJS environments' exports
-    module.exports.QUnit = QUnit;
-
-    exportedModule = true;
-  }
-
-  // For CommonJS with exports, but without module.exports, like Rhino
-  if (typeof exports !== 'undefined' && exports) {
-    exports.QUnit = QUnit;
-
-    exportedModule = true;
-  }
-
-  // For other environments, including Web Workers (globalThis === self),
-  // SpiderMonkey (mozjs), and other embedded JavaScript engines
-  if (!exportedModule) {
-    globalThis.QUnit = QUnit;
-  }
-}
diff --git a/src/qunit.js b/src/qunit.js
index 1f9cbccd5..c69c62ad0 100644
--- a/src/qunit.js
+++ b/src/qunit.js
@@ -1,7 +1,60 @@
-import QUnit from './core';
+/* global module, exports */
+
+import core from './core';
 import { initBrowser } from './browser/browser-runner';
-import { window, document } from './globals';
+import { globalThis, window, document } from './globals';
+
+/**
+ * Available exports:
+ *
+ * globalThis:
+ * - browser (globalThis === window)
+ * - Web Worker (globalThis === self)
+ * - Node.js
+ * - SpiderMonkey (mozjs)
+ * - Rhino 7.14+
+ * - any other embedded JS engine
+ *
+ * CommonJS module.exports (commonjs2):
+ * - Node.js
+ *
+ * CommonJS exports (commonjs, https://wiki.commonjs.org/wiki/Modules):
+ * - Rhino
+ */
+
+// If a real QUnit global was already defined, then replace our reference
+// with that one, and export that instead. Skip initBrowser() to avoid
+// doubling the user interface.
+//
+// Since QUnit 3.0, we no longer throw an error if QUnit is loaded twice.
+// This enables mixed use of ESM import and CJS require() in a project,
+// without split-brain problems for defining tests, setting config, registering
+// reporters, etc.
+//
+// Note that a placeholder QUnit global may exist for preconfiguration.
+// Such placeholder is recognised by not having QUnit.version (it should
+// only contain QUnit.config), and will be upgraded to the real QUnit.
+let QUnit;
+if (globalThis.QUnit && globalThis.QUnit.version) {
+  QUnit = globalThis.QUnit;
+} else {
+  QUnit = core;
+  globalThis.QUnit = QUnit;
+
+  if (window && document) {
+    initBrowser(QUnit, window, document);
+  }
+}
+
+// For Node.js
+if (typeof module !== 'undefined' && module && module.exports) {
+  module.exports = QUnit;
+
+  // For consistency with CommonJS environments' exports
+  module.exports.QUnit = QUnit;
+}
 
-if (window && document) {
-  initBrowser(QUnit, window, document);
+// For CommonJS with exports, but without module.exports, like Rhino
+if (typeof exports !== 'undefined' && exports) {
+  exports.QUnit = QUnit;
 }
diff --git a/test/benchmark/index-node.js b/test/benchmark/index-node.js
index 140edb11f..f8f17e284 100644
--- a/test/benchmark/index-node.js
+++ b/test/benchmark/index-node.js
@@ -1,6 +1,6 @@
 /* eslint-env node */
 
-global.QUnit = require('qunit');
+require('qunit');
 
 if (process.argv[2] === 'fast-deep-equal') {
   const fde = require('fast-deep-equal/es6');