diff --git a/.babelrc.js b/.babelrc.js
index 32c0360eac..ef46ad4e72 100644
--- a/.babelrc.js
+++ b/.babelrc.js
@@ -15,5 +15,41 @@ module.exports = {
     mjs: {
       presets: [['@babel/preset-env', { modules: false }]],
     },
+    esm: {
+      presets: [['@babel/preset-env', { modules: false }]],
+      plugins: [
+        function({ types }) {
+          return {
+            visitor: {
+              ImportDeclaration: function(path, state) {
+                if (!path.node.source) return;
+                var source = path.node.source.value;
+                if (source.match(/^\.{0,2}\//) && !source.endsWith('.es.js')) {
+                  path.replaceWith(
+                    types.importDeclaration(
+                      path.node.specifiers,
+                      types.stringLiteral(source + '.es.js'),
+                    ),
+                  );
+                }
+              },
+              ExportNamedDeclaration: function(path, state) {
+                if (!path.node.source) return;
+                const source = path.node.source.value;
+                if (source.match(/^\.{0,2}\//) && !source.endsWith('.es.js')) {
+                  path.replaceWith(
+                    types.exportNamedDeclaration(
+                      path.node.declaration,
+                      path.node.specifiers,
+                      types.stringLiteral(source + '.es.js'),
+                    ),
+                  );
+                }
+              },
+            },
+          };
+        },
+      ],
+    },
   },
 };
diff --git a/resources/build.js b/resources/build.js
index c1cc17a8de..bcbe830396 100644
--- a/resources/build.js
+++ b/resources/build.js
@@ -101,6 +101,7 @@ function buildJSFile(filepath) {
   copyFile(srcPath, destPath + '.flow');
   writeFile(destPath, babelBuild(srcPath, 'cjs'));
   writeFile(destPath.replace(/\.js$/, '.mjs'), babelBuild(srcPath, 'mjs'));
+  writeFile(destPath.replace(/\.js$/, '.es.js'), babelBuild(srcPath, 'esm'));
 }
 
 function buildPackageJSON() {
diff --git a/src/execution/execute.js b/src/execution/execute.js
index 8059719508..f6d5e18cfb 100644
--- a/src/execution/execute.js
+++ b/src/execution/execute.js
@@ -1,6 +1,6 @@
 // @flow strict
 
-import { forEach, isCollection } from 'iterall';
+import { forEach, isCollection } from '../jsutils/iterall';
 
 import inspect from '../jsutils/inspect';
 import memoize3 from '../jsutils/memoize3';
diff --git a/src/index.js b/src/index.js
index 4c1945ec56..c266250114 100644
--- a/src/index.js
+++ b/src/index.js
@@ -125,7 +125,7 @@ export {
   // Validate GraphQL schema.
   validateSchema,
   assertValidSchema,
-} from './type';
+} from './type/index';
 
 export type {
   GraphQLType,
@@ -168,7 +168,7 @@ export type {
   GraphQLScalarSerializer,
   GraphQLScalarValueParser,
   GraphQLScalarLiteralParser,
-} from './type';
+} from './type/index';
 
 // Parse and operate on GraphQL language source files.
 export {
@@ -204,7 +204,7 @@ export {
   isTypeDefinitionNode,
   isTypeSystemExtensionNode,
   isTypeExtensionNode,
-} from './language';
+} from './language/index';
 
 export type {
   ParseOptions,
@@ -276,7 +276,7 @@ export type {
   UnionTypeExtensionNode,
   EnumTypeExtensionNode,
   InputObjectTypeExtensionNode,
-} from './language';
+} from './language/index';
 
 // Execute GraphQL queries.
 export {
@@ -285,12 +285,12 @@ export {
   defaultTypeResolver,
   responsePathAsArray,
   getDirectiveValues,
-} from './execution';
+} from './execution/index';
 
-export type { ExecutionArgs, ExecutionResult } from './execution';
+export type { ExecutionArgs, ExecutionResult } from './execution/index';
 
-export { subscribe, createSourceEventStream } from './subscription';
-export type { SubscriptionArgs } from './subscription';
+export { subscribe, createSourceEventStream } from './subscription/index';
+export type { SubscriptionArgs } from './subscription/index';
 
 // Validate GraphQL documents.
 export {
@@ -324,9 +324,9 @@ export {
   ValuesOfCorrectTypeRule,
   VariablesAreInputTypesRule,
   VariablesInAllowedPositionRule,
-} from './validation';
+} from './validation/index';
 
-export type { ValidationRule } from './validation';
+export type { ValidationRule } from './validation/index';
 
 // Create, format, and print GraphQL errors.
 export {
@@ -335,9 +335,9 @@ export {
   locatedError,
   printError,
   formatError,
-} from './error';
+} from './error/index';
 
-export type { GraphQLFormattedError } from './error';
+export type { GraphQLFormattedError } from './error/index';
 
 // Utilities for operating on GraphQL type schema and parsed sources.
 export {
@@ -406,7 +406,7 @@ export {
   findDangerousChanges,
   // Report all deprecated usage within a GraphQL document.
   findDeprecatedUsages,
-} from './utilities';
+} from './utilities/index';
 
 export type {
   IntrospectionOptions,
@@ -434,4 +434,4 @@ export type {
   BuildSchemaOptions,
   BreakingChange,
   DangerousChange,
-} from './utilities';
+} from './utilities/index';
diff --git a/src/jsutils/instanceOf.js b/src/jsutils/instanceOf.js
index 967969ab21..aac7b9d93e 100644
--- a/src/jsutils/instanceOf.js
+++ b/src/jsutils/instanceOf.js
@@ -11,7 +11,8 @@ declare function instanceOf(
 
 // See: https://expressjs.com/en/advanced/best-practice-performance.html#set-node_env-to-production
 // See: https://webpack.js.org/guides/production/
-export default process.env.NODE_ENV === 'production'
+export default typeof process !== 'undefined' &&
+process.env.NODE_ENV === 'production'
   ? // eslint-disable-next-line no-shadow
     function instanceOf(value: mixed, constructor: mixed) {
       return value instanceof constructor;
diff --git a/src/jsutils/iterall.js b/src/jsutils/iterall.js
new file mode 100644
index 0000000000..736792731c
--- /dev/null
+++ b/src/jsutils/iterall.js
@@ -0,0 +1,168 @@
+// @flow strict
+
+const SYMBOL = typeof Symbol === 'function' ? Symbol : undefined;
+const SYMBOL_ITERATOR = SYMBOL && SYMBOL.iterator;
+const SYMBOL_ASYNC_ITERATOR = SYMBOL && SYMBOL.asyncIterator;
+
+function AsyncFromSyncIterator(iterator) {
+  this._i = iterator;
+}
+
+AsyncFromSyncIterator.prototype[$$asyncIterator] = function() {
+  return this;
+};
+
+AsyncFromSyncIterator.prototype.next = function() {
+  const step = this._i.next();
+  return Promise.resolve(step.value).then(value => ({
+    value,
+    done: step.done,
+  }));
+};
+
+function ArrayLikeIterator(obj) {
+  this._o = obj;
+  this._i = 0;
+}
+
+ArrayLikeIterator.prototype[$$iterator] = function() {
+  return this;
+};
+
+ArrayLikeIterator.prototype.next = function() {
+  if (this._o === undefined || this._i >= this._o.length) {
+    this._o = undefined;
+    return { value: undefined, done: true };
+  }
+  return { value: this._o[this._i++], done: false };
+};
+
+export const $$iterator = SYMBOL_ITERATOR || '@@iterator';
+
+export function isIterable(obj) {
+  return Boolean(getIteratorMethod(obj));
+}
+
+export function isArrayLike(obj) {
+  const length = obj != null && obj.length;
+  return typeof length === 'number' && length >= 0 && length % 1 === 0;
+}
+
+export function isCollection(obj) {
+  return Object(obj) === obj && (isArrayLike(obj) || isIterable(obj));
+}
+
+export function getIterator(iterable) {
+  const method = getIteratorMethod(iterable);
+  if (method) {
+    return method.call(iterable);
+  }
+}
+
+export function getIteratorMethod(iterable) {
+  if (iterable != null) {
+    const method =
+      (SYMBOL_ITERATOR && iterable[SYMBOL_ITERATOR]) || iterable['@@iterator'];
+    if (typeof method === 'function') {
+      return method;
+    }
+  }
+}
+
+export function createIterator(collection) {
+  if (collection != null) {
+    const iterator = getIterator(collection);
+    if (iterator) {
+      return iterator;
+    }
+    if (isArrayLike(collection)) {
+      return new ArrayLikeIterator(collection);
+    }
+  }
+}
+
+export function forEach(collection, callback, thisArg) {
+  if (collection != null) {
+    if (typeof collection.forEach === 'function') {
+      return collection.forEach(callback, thisArg);
+    }
+    let i = 0;
+    const iterator = getIterator(collection);
+    if (iterator) {
+      let step;
+      while (!(step = iterator.next()).done) {
+        callback.call(thisArg, step.value, i++, collection);
+        if (i > 9999999) {
+          throw new TypeError('Near-infinite iteration.');
+        }
+      }
+    } else if (isArrayLike(collection)) {
+      for (; i < collection.length; i++) {
+        if (Object.prototype.hasOwnProperty.call(collection, i)) {
+          callback.call(thisArg, collection[i], i, collection);
+        }
+      }
+    }
+  }
+}
+
+export const $$asyncIterator = SYMBOL_ASYNC_ITERATOR || '@@asyncIterator';
+
+export const isAsyncIterable = obj => Boolean(getAsyncIteratorMethod(obj));
+
+export const getAsyncIterator = asyncIterable => {
+  const method = getAsyncIteratorMethod(asyncIterable);
+  if (method) {
+    return method.call(asyncIterable);
+  }
+};
+
+export const getAsyncIteratorMethod = asyncIterable => {
+  if (asyncIterable != null) {
+    const method =
+      (SYMBOL_ASYNC_ITERATOR && asyncIterable[SYMBOL_ASYNC_ITERATOR]) ||
+      asyncIterable['@@asyncIterator'];
+    if (typeof method === 'function') {
+      return method;
+    }
+  }
+};
+
+export const createAsyncIterator = source => {
+  if (source != null) {
+    const asyncIterator = getAsyncIterator(source);
+    if (asyncIterator) {
+      return asyncIterator;
+    }
+    const iterator = createIterator(source);
+    if (iterator) {
+      return new AsyncFromSyncIterator(iterator);
+    }
+  }
+};
+
+export const forAwaitEach = (source, callback, thisArg) => {
+  const asyncIterator = createAsyncIterator(source);
+  if (asyncIterator) {
+    let i = 0;
+    return new Promise((resolve, reject) => {
+      function next() {
+        asyncIterator
+          .next()
+          .then(step => {
+            if (!step.done) {
+              Promise.resolve(callback.call(thisArg, step.value, i++, source))
+                .then(next)
+                .catch(reject);
+            } else {
+              resolve();
+            }
+            return null;
+          })
+          .catch(reject);
+        return null;
+      }
+      next();
+    });
+  }
+};
diff --git a/src/subscription/__tests__/eventEmitterAsyncIterator.js b/src/subscription/__tests__/eventEmitterAsyncIterator.js
index ea0d0d30ca..8d7dcc36f6 100644
--- a/src/subscription/__tests__/eventEmitterAsyncIterator.js
+++ b/src/subscription/__tests__/eventEmitterAsyncIterator.js
@@ -1,7 +1,7 @@
 // @flow strict
 
 import type EventEmitter from 'events';
-import { $$asyncIterator } from 'iterall';
+import { $$asyncIterator } from '../../jsutils/iterall';
 
 /**
  * Create an AsyncIterator from an EventEmitter. Useful for mocking a
diff --git a/src/subscription/asyncIteratorReject.js b/src/subscription/asyncIteratorReject.js
index 4dad88da40..3a43495d6a 100644
--- a/src/subscription/asyncIteratorReject.js
+++ b/src/subscription/asyncIteratorReject.js
@@ -1,6 +1,6 @@
 // @flow strict
 
-import { $$asyncIterator } from 'iterall';
+import { $$asyncIterator } from '../jsutils/iterall';
 
 /**
  * Given an error, returns an AsyncIterable which will fail with that error.
diff --git a/src/subscription/mapAsyncIterator.js b/src/subscription/mapAsyncIterator.js
index e8cb4363c7..6fd59c0abc 100644
--- a/src/subscription/mapAsyncIterator.js
+++ b/src/subscription/mapAsyncIterator.js
@@ -1,6 +1,6 @@
 // @flow strict
 
-import { $$asyncIterator, getAsyncIterator } from 'iterall';
+import { $$asyncIterator, getAsyncIterator } from '../jsutils/iterall';
 
 import { type PromiseOrValue } from '../jsutils/PromiseOrValue';
 
diff --git a/src/subscription/subscribe.js b/src/subscription/subscribe.js
index 8958e74952..0460f028eb 100644
--- a/src/subscription/subscribe.js
+++ b/src/subscription/subscribe.js
@@ -1,6 +1,6 @@
 // @flow strict
 
-import { isAsyncIterable } from 'iterall';
+import { isAsyncIterable } from '../jsutils/iterall';
 
 import inspect from '../jsutils/inspect';
 import { addPath, pathToArray } from '../jsutils/Path';
diff --git a/src/utilities/astFromValue.js b/src/utilities/astFromValue.js
index e4972960a4..f4dc087b4c 100644
--- a/src/utilities/astFromValue.js
+++ b/src/utilities/astFromValue.js
@@ -1,6 +1,6 @@
 // @flow strict
 
-import { forEach, isCollection } from 'iterall';
+import { forEach, isCollection } from '../jsutils/iterall';
 
 import objectValues from '../polyfills/objectValues';
 
diff --git a/src/utilities/coerceInputValue.js b/src/utilities/coerceInputValue.js
index d7f6ca747a..19901acf32 100644
--- a/src/utilities/coerceInputValue.js
+++ b/src/utilities/coerceInputValue.js
@@ -1,6 +1,6 @@
 // @flow strict
 
-import { forEach, isCollection } from 'iterall';
+import { forEach, isCollection } from '../jsutils/iterall';
 
 import objectValues from '../polyfills/objectValues';