diff --git a/docs/pages/api-docs/avatar-group.json b/docs/pages/api-docs/avatar-group.json
index f267333fde1d97..a82432ee0a6a33 100644
--- a/docs/pages/api-docs/avatar-group.json
+++ b/docs/pages/api-docs/avatar-group.json
@@ -10,6 +10,7 @@
       },
       "default": "'medium'"
     },
+    "sx": { "type": { "name": "object" } },
     "variant": {
       "type": {
         "name": "union",
@@ -25,5 +26,5 @@
   "filename": "/packages/material-ui/src/AvatarGroup/AvatarGroup.js",
   "inheritance": null,
   "demos": "<ul><li><a href=\"/components/avatars/\">Avatars</a></li></ul>",
-  "styledComponent": false
+  "styledComponent": true
 }
diff --git a/docs/translations/api-docs/avatar-group/avatar-group.json b/docs/translations/api-docs/avatar-group/avatar-group.json
index 0fc78564fc67ce..cf50f9faa15e67 100644
--- a/docs/translations/api-docs/avatar-group/avatar-group.json
+++ b/docs/translations/api-docs/avatar-group/avatar-group.json
@@ -5,6 +5,7 @@
     "classes": "Override or extend the styles applied to the component. See <a href=\"#css\">CSS API</a> below for more details.",
     "max": "Max avatars to show before +x.",
     "spacing": "Spacing between avatars.",
+    "sx": "The system prop that allows defining system overrides as well as additional CSS styles. See the <a href=\"/system/basics/#the-sx-prop\">`sx` page</a> for more details.",
     "variant": "The variant to use."
   },
   "classDescriptions": {
diff --git a/packages/material-ui/src/AvatarGroup/AvatarGroup.d.ts b/packages/material-ui/src/AvatarGroup/AvatarGroup.d.ts
index 2a71f2b4319026..ad82cb1e187772 100644
--- a/packages/material-ui/src/AvatarGroup/AvatarGroup.d.ts
+++ b/packages/material-ui/src/AvatarGroup/AvatarGroup.d.ts
@@ -1,6 +1,7 @@
 import * as React from 'react';
-import { InternalStandardProps as StandardProps } from '@material-ui/core';
+import { InternalStandardProps as StandardProps, Theme } from '@material-ui/core';
 import { OverridableStringUnion } from '@material-ui/types';
+import { SxProps } from '@material-ui/system';
 
 export interface AvatarGroupPropsVariantOverrides {}
 export type AvatarGroupVariantDefaults = Record<'circular' | 'rounded' | 'square', true>;
@@ -29,6 +30,10 @@ export interface AvatarGroupProps extends StandardProps<React.HTMLAttributes<HTM
    * @default 'medium'
    */
   spacing?: 'small' | 'medium' | number;
+  /**
+   * The system prop that allows defining system overrides as well as additional CSS styles.
+   */
+  sx?: SxProps<Theme>;
   /**
    * The variant to use.
    * @default 'circular'
diff --git a/packages/material-ui/src/AvatarGroup/AvatarGroup.js b/packages/material-ui/src/AvatarGroup/AvatarGroup.js
index 7597deb044bb50..4b49b1099c4ac0 100644
--- a/packages/material-ui/src/AvatarGroup/AvatarGroup.js
+++ b/packages/material-ui/src/AvatarGroup/AvatarGroup.js
@@ -2,36 +2,74 @@ import * as React from 'react';
 import PropTypes from 'prop-types';
 import { isFragment } from 'react-is';
 import clsx from 'clsx';
-import { chainPropTypes } from '@material-ui/utils';
-import { withStyles } from '../styles';
+import { chainPropTypes, deepmerge } from '@material-ui/utils';
+import { unstable_composeClasses as composeClasses } from '@material-ui/unstyled';
+import experimentalStyled from '../styles/experimentalStyled';
+import useThemeProps from '../styles/useThemeProps';
 import Avatar from '../Avatar';
+import { getAvatarGroupUtilityClass } from './avatarGroupClasses';
 
 const SPACINGS = {
   small: -16,
   medium: null,
 };
 
-export const styles = (theme) => ({
+const overridesResolver = (props, styles) => {
+  return deepmerge(styles.root || {}, {});
+};
+
+const useUtilityClasses = (styleProps) => {
+  const { classes } = styleProps;
+
+  const slots = {
+    root: ['root'],
+    avatar: ['avatar'],
+  };
+
+  return composeClasses(slots, getAvatarGroupUtilityClass, classes);
+};
+
+const AvatarGroupRoot = experimentalStyled(
+  'div',
+  {},
+  {
+    name: 'MuiAvatarGroup',
+    slot: 'Root',
+    overridesResolver,
+  }
+)({
   /* Styles applied to the root element. */
-  root: {
-    display: 'flex',
-    flexDirection: 'row-reverse',
+  display: 'flex',
+  flexDirection: 'row-reverse',
+});
+
+/* Styles applied to the avatar elements. */
+const AvatarGroupAvatar = experimentalStyled(
+  Avatar,
+  {},
+  {
+    name: 'MuiAvatarGroup',
+    slot: 'Avatar',
   },
-  /* Styles applied to the avatar elements. */
-  avatar: {
+)(
+  ({ theme }) => ({
     border: `2px solid ${theme.palette.background.default}`,
     boxSizing: 'content-box',
     marginLeft: -8,
     '&:last-child': {
       marginLeft: 0,
     },
-  },
-});
+  })
+);
+
+const AvatarGroup = React.forwardRef(function AvatarGroup(inProps, ref) {
+  const props = useThemeProps({
+    props: inProps,
+    name: 'MuiAvatarGroup',
+  });
 
-const AvatarGroup = React.forwardRef(function AvatarGroup(props, ref) {
   const {
     children: childrenProp,
-    classes,
     className,
     max = 5,
     spacing = 'medium',
@@ -40,6 +78,8 @@ const AvatarGroup = React.forwardRef(function AvatarGroup(props, ref) {
   } = props;
   const clampedMax = max < 2 ? 2 : max;
 
+  const classes = useUtilityClasses(props);
+
   const children = React.Children.toArray(childrenProp).filter((child) => {
     if (process.env.NODE_ENV !== 'production') {
       if (isFragment(child)) {
@@ -60,9 +100,9 @@ const AvatarGroup = React.forwardRef(function AvatarGroup(props, ref) {
   const marginLeft = spacing && SPACINGS[spacing] !== undefined ? SPACINGS[spacing] : -spacing;
 
   return (
-    <div className={clsx(classes.root, className)} ref={ref} {...other}>
+    <AvatarGroupRoot className={clsx(classes.root, className)} ref={ref} {...other}>
       {extraAvatars ? (
-        <Avatar
+        <AvatarGroupAvatar
           className={classes.avatar}
           style={{
             marginLeft,
@@ -70,7 +110,7 @@ const AvatarGroup = React.forwardRef(function AvatarGroup(props, ref) {
           variant={variant}
         >
           +{extraAvatars}
-        </Avatar>
+        </AvatarGroupAvatar>
       ) : null}
       {children
         .slice(0, children.length - extraAvatars)
@@ -85,7 +125,7 @@ const AvatarGroup = React.forwardRef(function AvatarGroup(props, ref) {
             variant: child.props.variant || variant,
           });
         })}
-    </div>
+    </AvatarGroupRoot>
   );
 });
 
@@ -125,6 +165,10 @@ AvatarGroup.propTypes = {
    * @default 'medium'
    */
   spacing: PropTypes.oneOfType([PropTypes.oneOf(['medium', 'small']), PropTypes.number]),
+  /**
+   * The system prop that allows defining system overrides as well as additional CSS styles.
+   */
+  sx: PropTypes.object,
   /**
    * The variant to use.
    * @default 'circular'
@@ -135,4 +179,4 @@ AvatarGroup.propTypes = {
   ]),
 };
 
-export default withStyles(styles, { name: 'MuiAvatarGroup' })(AvatarGroup);
+export default AvatarGroup;
diff --git a/packages/material-ui/src/AvatarGroup/AvatarGroup.test.js b/packages/material-ui/src/AvatarGroup/AvatarGroup.test.js
index 7e5e1e9af1a155..c719b46329db41 100644
--- a/packages/material-ui/src/AvatarGroup/AvatarGroup.test.js
+++ b/packages/material-ui/src/AvatarGroup/AvatarGroup.test.js
@@ -1,24 +1,21 @@
 import * as React from 'react';
 import { expect } from 'chai';
-import { getClasses, createMount, describeConformance, createClientRender } from 'test/utils';
+import { createMount, describeConformanceV5, createClientRender } from 'test/utils';
 import Avatar from '@material-ui/core/Avatar';
+import classes from './avatarGroupClasses';
 import AvatarGroup from './AvatarGroup';
 
 describe('<AvatarGroup />', () => {
   const mount = createMount();
-  let classes;
   const render = createClientRender();
 
-  before(() => {
-    classes = getClasses(<AvatarGroup />);
-  });
-
-  describeConformance(<AvatarGroup />, () => ({
+  describeConformanceV5(<AvatarGroup />, () => ({
     classes,
     inheritComponent: 'div',
     mount,
+    muiName: 'MuiAvatarGroup',
     refInstanceof: window.HTMLDivElement,
-    skip: ['componentProp'],
+    skip: ['componentsProp'],
   }));
 
   it('should display all the avatars', () => {
diff --git a/packages/material-ui/src/AvatarGroup/avatarGroupClasses.d.ts b/packages/material-ui/src/AvatarGroup/avatarGroupClasses.d.ts
new file mode 100644
index 00000000000000..94056d92ac61c4
--- /dev/null
+++ b/packages/material-ui/src/AvatarGroup/avatarGroupClasses.d.ts
@@ -0,0 +1,10 @@
+export interface AvatarGroupClasses {
+  root: string,
+  avatar: string,
+}
+
+declare const avatarGroupClasses: AvatarGroupClasses;
+
+export function getAvatarGroupUtilityClass(slot: string): string;
+
+export default avatarGroupClasses;
diff --git a/packages/material-ui/src/AvatarGroup/avatarGroupClasses.js b/packages/material-ui/src/AvatarGroup/avatarGroupClasses.js
new file mode 100644
index 00000000000000..0277a4d423f516
--- /dev/null
+++ b/packages/material-ui/src/AvatarGroup/avatarGroupClasses.js
@@ -0,0 +1,12 @@
+import { generateUtilityClass, generateUtilityClasses } from '@material-ui/unstyled';
+
+export function getAvatarGroupUtilityClass(slot) {
+  return generateUtilityClass('MuiAvatarGroup', slot);
+}
+
+const avatarGroupClasses = generateUtilityClasses('MuiAvatarGroup', [
+  'root',
+  'avatar',
+]);
+
+export default avatarGroupClasses;
diff --git a/packages/material-ui/src/AvatarGroup/index.d.ts b/packages/material-ui/src/AvatarGroup/index.d.ts
index a691e2cb2eff92..90c212c73f297a 100644
--- a/packages/material-ui/src/AvatarGroup/index.d.ts
+++ b/packages/material-ui/src/AvatarGroup/index.d.ts
@@ -1,2 +1,4 @@
 export { default } from './AvatarGroup';
 export * from './AvatarGroup';
+export { default as avatarGroupClasses } from './avatarGroupClasses';
+export * from './avatarGroupClasses';
\ No newline at end of file
diff --git a/packages/material-ui/src/AvatarGroup/index.js b/packages/material-ui/src/AvatarGroup/index.js
index 20c5443b297112..4b1648bd4782ef 100644
--- a/packages/material-ui/src/AvatarGroup/index.js
+++ b/packages/material-ui/src/AvatarGroup/index.js
@@ -1 +1,3 @@
 export { default } from './AvatarGroup';
+export { default as avatarGroupClasses } from './avatarGroupClasses';
+export * from './avatarGroupClasses';
\ No newline at end of file