diff --git a/packages/@ember/-internals/metal/index.ts b/packages/@ember/-internals/metal/index.ts
index 29417e57e85..c6f731aee75 100644
--- a/packages/@ember/-internals/metal/index.ts
+++ b/packages/@ember/-internals/metal/index.ts
@@ -4,13 +4,7 @@ export { default as alias } from './lib/alias';
 export { deprecateProperty } from './lib/deprecate_property';
 export { PROXY_CONTENT, _getPath, get, _getProp } from './lib/property_get';
 export { set, _setProp, trySet } from './lib/property_set';
-export {
-  objectAt,
-  replace,
-  replaceInNativeArray,
-  addArrayObserver,
-  removeArrayObserver,
-} from './lib/array';
+export { objectAt, replace, replaceInNativeArray } from './lib/array';
 export { arrayContentWillChange, arrayContentDidChange } from './lib/array_events';
 export { eachProxyArrayWillChange, eachProxyArrayDidChange } from './lib/each_proxy_events';
 export { addListener, hasListeners, on, removeListener, sendEvent } from './lib/events';
diff --git a/packages/@ember/-internals/metal/lib/array.ts b/packages/@ember/-internals/metal/lib/array.ts
index 92043a6128e..b1e866049dc 100644
--- a/packages/@ember/-internals/metal/lib/array.ts
+++ b/packages/@ember/-internals/metal/lib/array.ts
@@ -1,15 +1,8 @@
-import { EmberArray, getDebugName } from '@ember/-internals/utils';
-import { deprecate } from '@ember/debug';
+import { EmberArray } from '@ember/-internals/utils';
 import { arrayContentDidChange, arrayContentWillChange } from './array_events';
-import { addListener, removeListener } from './events';
-import { notifyPropertyChange } from './property_events';
 
 const EMPTY_ARRAY = Object.freeze([]);
 
-interface ObjectHasArrayObservers {
-  hasArrayObservers?: boolean;
-}
-
 export function objectAt<T>(array: T[] | EmberArray<T>, index: number): T | undefined {
   if (Array.isArray(array)) {
     return array[index];
@@ -56,84 +49,3 @@ export function replaceInNativeArray<T>(
 
   arrayContentDidChange(array, start, deleteCount, items.length);
 }
-
-interface ArrayObserverOptions {
-  willChange?: string;
-  didChange?: string;
-}
-
-type Operation = (
-  obj: ObjectHasArrayObservers,
-  eventName: string,
-  target: object | Function | null,
-  callbackName: string
-) => void;
-
-function arrayObserversHelper(
-  obj: ObjectHasArrayObservers,
-  target: object | Function | null,
-  opts: ArrayObserverOptions | undefined,
-  operation: Operation,
-  notify: boolean
-): ObjectHasArrayObservers {
-  let willChange = (opts && opts.willChange) || 'arrayWillChange';
-  let didChange = (opts && opts.didChange) || 'arrayDidChange';
-  let hasObservers = obj.hasArrayObservers;
-
-  operation(obj, '@array:before', target, willChange);
-  operation(obj, '@array:change', target, didChange);
-
-  if (hasObservers === notify) {
-    notifyPropertyChange(obj, 'hasArrayObservers');
-  }
-
-  return obj;
-}
-
-export function addArrayObserver<T>(
-  array: EmberArray<T>,
-  target: object | Function | null,
-  opts?: ArrayObserverOptions | undefined,
-  suppress = false
-): ObjectHasArrayObservers {
-  deprecate(
-    `Array observers have been deprecated. Added an array observer to ${getDebugName?.(array)}.`,
-    suppress,
-    {
-      id: 'array-observers',
-      url: 'https://deprecations.emberjs.com/v3.x#toc_array-observers',
-      until: '4.0.0',
-      for: 'ember-source',
-      since: {
-        enabled: '3.26.0-beta.1',
-      },
-    }
-  );
-
-  return arrayObserversHelper(array, target, opts, addListener, false);
-}
-
-export function removeArrayObserver<T>(
-  array: EmberArray<T>,
-  target: object | Function | null,
-  opts?: ArrayObserverOptions | undefined,
-  suppress = false
-): ObjectHasArrayObservers {
-  deprecate(
-    `Array observers have been deprecated. Removed an array observer from ${getDebugName?.(
-      array
-    )}.`,
-    suppress,
-    {
-      id: 'array-observers',
-      url: 'https://deprecations.emberjs.com/v3.x#toc_array-observers',
-      until: '4.0.0',
-      for: 'ember-source',
-      since: {
-        enabled: '3.26.0-beta.1',
-      },
-    }
-  );
-
-  return arrayObserversHelper(array, target, opts, removeListener, true);
-}
diff --git a/packages/@ember/-internals/metal/lib/array_events.ts b/packages/@ember/-internals/metal/lib/array_events.ts
index ee7c73285c5..56e160c75da 100644
--- a/packages/@ember/-internals/metal/lib/array_events.ts
+++ b/packages/@ember/-internals/metal/lib/array_events.ts
@@ -1,5 +1,4 @@
 import { peekMeta } from '@ember/-internals/meta';
-import { sendEvent } from './events';
 import { notifyPropertyChange } from './property_events';
 
 export function arrayContentWillChange<T extends object>(
@@ -22,8 +21,6 @@ export function arrayContentWillChange<T extends object>(
     }
   }
 
-  sendEvent(array, '@array:before', [array, startIdx, removeAmt, addAmt]);
-
   return array;
 }
 
@@ -58,8 +55,6 @@ export function arrayContentDidChange<T extends { length: number }>(
     notifyPropertyChange(array, '[]', meta);
   }
 
-  sendEvent(array, '@array:change', [array, startIdx, removeAmt, addAmt]);
-
   if (meta !== null) {
     let length = array.length;
     let addedAmount = addAmt === -1 ? 0 : addAmt;
diff --git a/packages/@ember/-internals/runtime/lib/mixins/array.js b/packages/@ember/-internals/runtime/lib/mixins/array.js
index d934edc8ba9..6ac0376e20a 100644
--- a/packages/@ember/-internals/runtime/lib/mixins/array.js
+++ b/packages/@ember/-internals/runtime/lib/mixins/array.js
@@ -12,14 +12,10 @@ import {
   replace,
   computed,
   Mixin,
-  hasListeners,
   beginPropertyChanges,
   endPropertyChanges,
-  addArrayObserver,
-  removeArrayObserver,
   arrayContentWillChange,
   arrayContentDidChange,
-  nativeDescDecorator as descriptor,
 } from '@ember/-internals/metal';
 import { assert } from '@ember/debug';
 import Enumerable from './enumerable';
@@ -476,106 +472,6 @@ const ArrayMixin = Mixin.create(Enumerable, {
     return -1;
   },
 
-  // ..........................................................
-  // ARRAY OBSERVERS
-  //
-
-  /**
-    Adds an array observer to the receiving array. The array observer object
-    normally must implement two methods:
-
-    * `willChange(observedObj, start, removeCount, addCount)` - This method will be
-      called just before the array is modified.
-    * `didChange(observedObj, start, removeCount, addCount)` - This method will be
-      called just after the array is modified.
-
-    Both callbacks will be passed the observed object, starting index of the
-    change as well as a count of the items to be removed and added. You can use
-    these callbacks to optionally inspect the array during the change, clear
-    caches, or do any other bookkeeping necessary.
-
-    In addition to passing a target, you can also include an options hash
-    which you can use to override the method names that will be invoked on the
-    target.
-
-    @method addArrayObserver
-    @param {Object} target The observer object.
-    @param {Object} opts Optional hash of configuration options including
-      `willChange` and `didChange` option.
-    @return {EmberArray} receiver
-    @public
-    @example
-        import Service from '@ember/service';
-
-        export default Service.extend({
-          data: Ember.A(),
-
-          init() {
-            this._super(...arguments);
-
-            this.data.addArrayObserver(this, {
-              willChange: 'dataWillChange',
-              didChange: 'dataDidChange'
-            });
-          },
-
-          dataWillChange(array, start, removeCount, addCount) {
-            console.log('array will change', array, start, removeCount, addCount);
-          },
-
-          dataDidChange(array, start, removeCount, addCount) {
-            console.log('array did change', array, start, removeCount, addCount);
-          }
-        });
-  */
-
-  addArrayObserver(target, opts) {
-    return addArrayObserver(this, target, opts);
-  },
-
-  /**
-    Removes an array observer from the object if the observer is current
-    registered. Calling this method multiple times with the same object will
-    have no effect.
-
-    @method removeArrayObserver
-    @param {Object} target The object observing the array.
-    @param {Object} opts Optional hash of configuration options including
-      `willChange` and `didChange` option.
-    @return {EmberArray} receiver
-    @public
-  */
-  removeArrayObserver(target, opts) {
-    return removeArrayObserver(this, target, opts);
-  },
-
-  /**
-    Becomes true whenever the array currently has observers watching changes
-    on the array.
-
-    ```javascript
-    let arr = [1, 2, 3, 4, 5];
-    arr.hasArrayObservers; // false
-
-    arr.addArrayObserver(this, {
-      willChange() {
-        console.log('willChange');
-      }
-    });
-    arr.hasArrayObservers; // true
-    ```
-
-    @property {Boolean} hasArrayObservers
-    @public
-  */
-  hasArrayObservers: descriptor({
-    configurable: true,
-    enumerable: false,
-    get() {
-      return hasListeners(this, '@array:change') || hasListeners(this, '@array:before');
-    },
-  }),
-
   /**
     If you are implementing an object that supports `EmberArray`, call this
     method just before the array content changes to notify any observers and
@@ -583,51 +479,46 @@ const ArrayMixin = Mixin.create(Enumerable, {
     as well as a delta of the amounts to change.
 
     ```app/components/show-post.js
-    import Component from '@ember/component';
-    import EmberObject from '@ember/object';
+    import Component from '@glimmer/component';
+    import EmberObject, { action } from '@ember/object';
+    import { tracked } from '@glimmer/tracking';
 
     const Post = EmberObject.extend({
+      successfulModifications: 0,
+
       body: '',
       save() {}
+
+      length: computed(function() {
+        this.incrementProperty('successfulModifications');
+      }),
     })
 
-    export default Component.extend({
-      attemptsToModify: 0,
-      successfulModifications: 0,
-      posts: null,
+    export default class ShowPost extends Component {
+      posts = null;
 
-      init() {
-        this._super(...arguments);
+      constructor() {
+        super(...arguments);
 
         this.posts = [1, 2, 3].map(i => Post.create({ body: i }));
-        this.posts.addArrayObserver(this, {
-          willChange() {
-            this.incrementProperty('attemptsToModify');
-          },
-          didChange() {
-            this.incrementProperty('successfulModifications');
-          }
-        });
-      },
-
-      actions: {
-        editPost(post, newContent) {
-          let oldContent = post.body,
-              postIndex = this.posts.indexOf(post);
-
-          this.posts.arrayContentWillChange(postIndex, 0, 0); // attemptsToModify = 1
-          post.set('body', newContent);
-
-          post.save()
-            .then(response => {
-              this.posts.arrayContentDidChange(postIndex, 0, 0); // successfulModifications = 1
-            })
-            .catch(error => {
-              post.set('body', oldContent);
-            })
-        }
       }
-    });
+
+      @action
+      editPost(post, newContent) {
+        let oldContent = post.body;
+        let postIndex = this.posts.indexOf(post);
+
+        post.body = newContent;
+
+        post.save()
+          .then(response => {
+            this.posts.arrayContentDidChange(postIndex, 0, 0); // post.successfulModifications = 1
+          })
+          .catch(error => {
+            post.body = oldContent;
+          })
+      }
+    }
     ```
 
     @method arrayContentWillChange
diff --git a/packages/@ember/-internals/runtime/lib/system/array_proxy.js b/packages/@ember/-internals/runtime/lib/system/array_proxy.js
index 8fed955c0a9..d099c79ced4 100644
--- a/packages/@ember/-internals/runtime/lib/system/array_proxy.js
+++ b/packages/@ember/-internals/runtime/lib/system/array_proxy.js
@@ -7,11 +7,11 @@ import {
   objectAt,
   alias,
   PROPERTY_DID_CHANGE,
-  addArrayObserver,
-  removeArrayObserver,
   replace,
   arrayContentDidChange,
   tagForProperty,
+  addListener,
+  removeListener,
 } from '@ember/-internals/metal';
 import { isObject } from '@ember/-internals/utils';
 import EmberObject from './object';
@@ -25,6 +25,28 @@ const ARRAY_OBSERVER_MAPPING = {
   didChange: '_arrangedContentArrayDidChange',
 };
 
+// Mimic behaviour in old addArrayObserver, but smplified.
+function addArrayObserver(obj, target, opts) {
+  let willChange = (opts && opts.willChange) || 'arrayWillChange';
+  let didChange = (opts && opts.didChange) || 'arrayDidChange';
+
+  addListener(obj, '@array:before', target, willChange);
+  addListener(obj, '@array:change', target, didChange);
+
+  return obj;
+}
+
+// Mimic behaviour in old addArrayObserver, but smplified.
+function removeArrayObserver(obj, target, opts) {
+  let willChange = (opts && opts.willChange) || 'arrayWillChange';
+  let didChange = (opts && opts.didChange) || 'arrayDidChange';
+
+  removeListener(obj, '@array:before', target, willChange);
+  removeListener(obj, '@array:change', target, didChange);
+
+  return obj;
+}
+
 function customTagForArrayProxy(proxy, key) {
   if (key === '[]') {
     proxy._revalidate();
diff --git a/packages/@ember/-internals/runtime/tests/helpers/array.js b/packages/@ember/-internals/runtime/tests/helpers/array.js
index 0f5f5008d38..737c8a3b63b 100644
--- a/packages/@ember/-internals/runtime/tests/helpers/array.js
+++ b/packages/@ember/-internals/runtime/tests/helpers/array.js
@@ -4,8 +4,6 @@ import { generateGuid, guidFor } from '@ember/-internals/utils';
 import {
   get,
   computed,
-  addArrayObserver,
-  removeArrayObserver,
   arrayContentWillChange,
   arrayContentDidChange,
 } from '@ember/-internals/metal';
@@ -60,16 +58,6 @@ const ArrayTestsObserverClass = EmberObject.extend({
     return this;
   },
 
-  observeArray(obj) {
-    addArrayObserver(obj, this);
-    return this;
-  },
-
-  stopObserveArray(obj) {
-    removeArrayObserver(obj, this);
-    return this;
-  },
-
   propertyDidChange(target, key, value) {
     if (this._keys[key] === undefined) {
       this._keys[key] = 0;
diff --git a/packages/@ember/-internals/runtime/tests/mixins/array_test.js b/packages/@ember/-internals/runtime/tests/mixins/array_test.js
index 49b158919ae..47214246e47 100644
--- a/packages/@ember/-internals/runtime/tests/mixins/array_test.js
+++ b/packages/@ember/-internals/runtime/tests/mixins/array_test.js
@@ -5,8 +5,6 @@ import {
   addObserver,
   observer as emberObserver,
   computed,
-  addArrayObserver,
-  removeArrayObserver,
   arrayContentDidChange,
   arrayContentWillChange,
 } from '@ember/-internals/metal';
@@ -196,8 +194,6 @@ moduleFor(
   'notify array observers',
   class extends AbstractTestCase {
     beforeEach(assert) {
-      expectDeprecation(/Array observers have been deprecated/);
-
       obj = DummyArray.create();
 
       observer = EmberObject.extend({
@@ -214,8 +210,6 @@ moduleFor(
         _before: null,
         _after: null,
       });
-
-      addArrayObserver(obj, observer);
     }
 
     afterEach() {
@@ -246,31 +240,6 @@ moduleFor(
       arrayContentDidChange(obj, 0, 2, 1);
       assert.deepEqual(observer._after, [obj, 0, 2, 1]);
     }
-
-    ['@test removing array observer should disable'](assert) {
-      removeArrayObserver(obj, observer);
-      arrayContentWillChange(obj);
-      assert.deepEqual(observer._before, null);
-
-      arrayContentDidChange(obj);
-      assert.deepEqual(observer._after, null);
-    }
-
-    ['@test hasArrayObservers should work'](assert) {
-      assert.equal(
-        obj.hasArrayObservers,
-        true,
-        'correctly shows it has an array observer when one exists'
-      );
-
-      removeArrayObserver(obj, observer);
-
-      assert.equal(
-        obj.hasArrayObservers,
-        false,
-        'correctly shows it has an array observer when one exists'
-      );
-    }
   }
 );
 
diff --git a/packages/@ember/-internals/runtime/tests/mutable-array/replace-test.js b/packages/@ember/-internals/runtime/tests/mutable-array/replace-test.js
index afa44afd6f2..8d684149895 100644
--- a/packages/@ember/-internals/runtime/tests/mutable-array/replace-test.js
+++ b/packages/@ember/-internals/runtime/tests/mutable-array/replace-test.js
@@ -241,8 +241,6 @@ class ReplaceTests extends AbstractTestCase {
   }
 
   async '@test Adding object should notify array observer'() {
-    expectDeprecation(/Array observers have been deprecated/);
-
     let fixtures = newFixture(4);
     let obj = this.newObject(fixtures);
     let observer = this.newObserver(obj).observeArray(obj);
diff --git a/packages/@ember/-internals/runtime/tests/system/array_proxy/array_observer_test.js b/packages/@ember/-internals/runtime/tests/system/array_proxy/array_observer_test.js
deleted file mode 100644
index 8515d192521..00000000000
--- a/packages/@ember/-internals/runtime/tests/system/array_proxy/array_observer_test.js
+++ /dev/null
@@ -1,55 +0,0 @@
-import { set } from '@ember/-internals/metal';
-import ArrayProxy from '../../../lib/system/array_proxy';
-import { A } from '../../../lib/mixins/array';
-import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
-
-moduleFor(
-  'ArrayProxy - array observers',
-  class extends AbstractTestCase {
-    ['@test mutating content'](assert) {
-      expectDeprecation(/Array observers have been deprecated/);
-
-      assert.expect(5);
-
-      let content = A(['x', 'y', 'z']);
-      let proxy = ArrayProxy.create({ content });
-
-      proxy.addArrayObserver({
-        arrayWillChange(proxy, startIndex, removeCount, addCount) {
-          assert.deepEqual([startIndex, removeCount, addCount], [1, 1, 3]);
-          assert.deepEqual(proxy.toArray(), ['x', 'y', 'z']);
-        },
-        arrayDidChange(proxy, startIndex, removeCount, addCount) {
-          assert.deepEqual([startIndex, removeCount, addCount], [1, 1, 3]);
-          assert.deepEqual(proxy.toArray(), ['x', 'a', 'b', 'c', 'z']);
-        },
-      });
-
-      proxy.toArray();
-      content.replace(1, 1, ['a', 'b', 'c']);
-    }
-
-    ['@test assigning content'](assert) {
-      expectDeprecation(/Array observers have been deprecated/);
-
-      assert.expect(5);
-
-      let content = A(['x', 'y', 'z']);
-      let proxy = ArrayProxy.create({ content });
-
-      proxy.addArrayObserver({
-        arrayWillChange(proxy, startIndex, removeCount, addCount) {
-          assert.deepEqual([startIndex, removeCount, addCount], [0, 3, 5]);
-          assert.deepEqual(proxy.toArray(), ['x', 'y', 'z']);
-        },
-        arrayDidChange(proxy, startIndex, removeCount, addCount) {
-          assert.deepEqual([startIndex, removeCount, addCount], [0, 3, 5]);
-          assert.deepEqual(proxy.toArray(), ['a', 'b', 'c', 'd', 'e']);
-        },
-      });
-
-      proxy.toArray();
-      set(proxy, 'content', A(['a', 'b', 'c', 'd', 'e']));
-    }
-  }
-);
diff --git a/packages/@ember/-internals/runtime/tests/system/array_proxy/watching_and_listening_test.js b/packages/@ember/-internals/runtime/tests/system/array_proxy/watching_and_listening_test.js
deleted file mode 100644
index 0717a429bd7..00000000000
--- a/packages/@ember/-internals/runtime/tests/system/array_proxy/watching_and_listening_test.js
+++ /dev/null
@@ -1,66 +0,0 @@
-import { peekMeta } from '@ember/-internals/meta';
-import ArrayProxy from '../../../lib/system/array_proxy';
-import { A } from '../../../lib/mixins/array';
-import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
-
-function sortedListenersFor(obj, eventName) {
-  let listeners = peekMeta(obj).matchingListeners(eventName) || [];
-
-  let keys = [];
-  for (let i = 0; i < listeners.length; i += 3) {
-    keys.push(listeners[i + 1]);
-  }
-  return keys.sort();
-}
-
-moduleFor(
-  'ArrayProxy - watching and listening',
-  class extends AbstractTestCase {
-    [`@test setting 'content' adds listeners correctly`](assert) {
-      let content = A();
-      let proxy = ArrayProxy.create();
-
-      assert.deepEqual(sortedListenersFor(content, '@array:before'), []);
-      assert.deepEqual(sortedListenersFor(content, '@array:change'), []);
-
-      proxy.set('content', content);
-
-      assert.deepEqual(sortedListenersFor(content, '@array:before'), [
-        '_arrangedContentArrayWillChange',
-      ]);
-      assert.deepEqual(sortedListenersFor(content, '@array:change'), [
-        '_arrangedContentArrayDidChange',
-      ]);
-    }
-
-    [`@test changing 'content' adds and removes listeners correctly`](assert) {
-      let content1 = A();
-      let content2 = A();
-      let proxy = ArrayProxy.create({ content: content1 });
-
-      assert.deepEqual(sortedListenersFor(content1, '@array:before'), []);
-      assert.deepEqual(sortedListenersFor(content1, '@array:change'), []);
-
-      // setup proxy
-      proxy.length;
-
-      assert.deepEqual(sortedListenersFor(content1, '@array:before'), [
-        '_arrangedContentArrayWillChange',
-      ]);
-      assert.deepEqual(sortedListenersFor(content1, '@array:change'), [
-        '_arrangedContentArrayDidChange',
-      ]);
-
-      proxy.set('content', content2);
-
-      assert.deepEqual(sortedListenersFor(content1, '@array:before'), []);
-      assert.deepEqual(sortedListenersFor(content1, '@array:change'), []);
-      assert.deepEqual(sortedListenersFor(content2, '@array:before'), [
-        '_arrangedContentArrayWillChange',
-      ]);
-      assert.deepEqual(sortedListenersFor(content2, '@array:change'), [
-        '_arrangedContentArrayDidChange',
-      ]);
-    }
-  }
-);
diff --git a/tests/docs/expected.js b/tests/docs/expected.js
index 54ac5a51513..d77b7f1c46d 100644
--- a/tests/docs/expected.js
+++ b/tests/docs/expected.js
@@ -58,7 +58,6 @@ module.exports = {
     'actions',
     'activate',
     'adapter',
-    'addArrayObserver',
     'addListener',
     'addObject',
     'addObjects',
@@ -248,7 +247,6 @@ module.exports = {
     'handleEvent',
     'handleURL',
     'has',
-    'hasArrayObservers',
     'has-block',
     'has-block-params',
     'hash',
@@ -418,7 +416,6 @@ module.exports = {
     'reject',
     'rejectBy',
     'releaseMethods',
-    'removeArrayObserver',
     'removeAt',
     'removeListener',
     'removeObject',