diff --git a/src/app/views/App.tsx b/src/app/views/App.tsx
index f9473bc26c..6721078946 100644
--- a/src/app/views/App.tsx
+++ b/src/app/views/App.tsx
@@ -425,8 +425,7 @@ class App extends Component<IAppProps, IAppState> {
     const fluentV9Themes: Record<string, Theme> = {
       'light': webLightTheme,
       'dark': webDarkTheme,
-      'high-contrast': teamsHighContrastTheme,
-      'system': getSystemTheme() === 'dark' ? webDarkTheme : webLightTheme
+      'high-contrast': teamsHighContrastTheme
     }
     return (
       // @ts-ignore
diff --git a/src/app/views/main-header/settings/ThemeChooserV9.tsx b/src/app/views/main-header/settings/ThemeChooserV9.tsx
index 0140a5ee4b..396d647749 100644
--- a/src/app/views/main-header/settings/ThemeChooserV9.tsx
+++ b/src/app/views/main-header/settings/ThemeChooserV9.tsx
@@ -23,11 +23,6 @@ const availableThemes = [
     key: 'high-contrast',
     displayName: 'Teams High Contrast',
     icon: <CircleHalfFillFilled />
-  },
-  {
-    key: 'system',
-    displayName: 'System Default',
-    icon: <SettingsFilled />
   }
 ];
 
diff --git a/src/themes/index.ts b/src/themes/index.ts
index f3b8349a8f..b7eacfa3eb 100644
--- a/src/themes/index.ts
+++ b/src/themes/index.ts
@@ -3,19 +3,11 @@ import { IPartialTheme, loadTheme } from '@fluentui/react';
 import { dark } from './dark';
 import { highContrast } from './high-contrast';
 import { light } from './light';
-// changes to be removed on cleanup
-const getSystemTheme = (): string => {
-  if (window.matchMedia && window.matchMedia('(prefers-color-scheme: dark)').matches) {
-    return 'dark';
-  }
-  return 'light';
-};
 
 const themes: any = {
   dark,
   light,
-  'high-contrast': highContrast,
-  system: getSystemTheme() === 'dark' ? dark : light
+  'high-contrast': highContrast
 };
 
 export function loadGETheme(theme: string): void {