diff --git a/src/common/components/DarkModeToggleButton.tsx b/src/common/components/DarkModeToggleButton.tsx
index 7ca93319d..60f010cad 100644
--- a/src/common/components/DarkModeToggleButton.tsx
+++ b/src/common/components/DarkModeToggleButton.tsx
@@ -1,8 +1,10 @@
 import * as React from 'react';
 
 import { Button, IconButton, useColorScheme } from '@mui/joy';
+import BrightnessAutoIcon from '@mui/icons-material/BrightnessAuto';
 import DarkModeIcon from '@mui/icons-material/DarkMode';
 import LightModeIcon from '@mui/icons-material/LightMode';
+import { GoodTooltip } from './GoodTooltip';
 
 export const darkModeToggleButtonSx = {
   boxShadow: 'sm',
@@ -12,29 +14,64 @@ export const darkModeToggleButtonSx = {
   },
 } as const;
 
+type ThemeMode = 'light' | 'dark' | 'system';
+
+const _nextThemeMode: Record<ThemeMode, ThemeMode> = {
+  light: 'dark',
+  dark: 'system',
+  system: 'light',
+};
+
+const _themeModeLabel: Record<ThemeMode, string> = {
+  light: 'Light Theme',
+  dark: 'Dark Theme',
+  system: 'System Theme',
+};
+
+function _themeModeIcon(mode: ThemeMode) {
+  switch (mode) {
+    case 'dark':
+      return <DarkModeIcon />;
+    case 'system':
+      return <BrightnessAutoIcon />;
+    case 'light':
+    default:
+      return <LightModeIcon />;
+  }
+}
+
 export function DarkModeToggleButton(props: { hasText?: boolean }) {
 
   // external state
   const { mode: colorMode, setMode: setColorMode } = useColorScheme();
+  const mode: ThemeMode = colorMode === 'light' || colorMode === 'dark' || colorMode === 'system'
+    ? colorMode
+    : 'system';
 
   const handleToggleDarkMode = (event: React.MouseEvent) => {
     event.stopPropagation();
-    setColorMode(colorMode === 'dark' ? 'light' : 'dark');
+    setColorMode(_nextThemeMode[mode]);
   };
 
-  return props.hasText ? (
-    <Button
-      variant='soft'
-      color='neutral'
-      onClick={handleToggleDarkMode}
-      sx={darkModeToggleButtonSx}
-      startDecorator={colorMode !== 'dark' ? <DarkModeIcon color='primary' /> : <LightModeIcon />}
-    >
-      {colorMode === 'dark' ? 'Light Mode' : 'Dark Mode'}
-    </Button>
-  ) : (
-    <IconButton size='sm' variant='soft' onClick={handleToggleDarkMode} sx={{ ml: 'auto', /*mr: '2px',*/ my: '-0.25rem' /* absorb the menuItem padding */ }}>
-      {colorMode !== 'dark' ? <DarkModeIcon /> : <LightModeIcon />}
-    </IconButton>
+  const title = `Theme: ${_themeModeLabel[mode]}`;
+
+  return (
+    <GoodTooltip title={title}>
+      {props.hasText ? (
+        <Button
+          variant='soft'
+          color='neutral'
+          onClick={handleToggleDarkMode}
+          sx={darkModeToggleButtonSx}
+          startDecorator={React.cloneElement(_themeModeIcon(mode), { color: 'primary' })}
+        >
+          {_themeModeLabel[mode]}
+        </Button>
+      ) : (
+        <IconButton size='sm' variant='soft' onClick={handleToggleDarkMode} sx={{ ml: 'auto', /*mr: '2px',*/ my: '-0.25rem' /* absorb the menuItem padding */ }}>
+          {_themeModeIcon(mode)}
+        </IconButton>
+      )}
+    </GoodTooltip>
   );
-}
\ No newline at end of file
+}
diff --git a/src/common/providers/ProviderTheming.tsx b/src/common/providers/ProviderTheming.tsx
index 1f75e185b..86b7e0b8b 100644
--- a/src/common/providers/ProviderTheming.tsx
+++ b/src/common/providers/ProviderTheming.tsx
@@ -61,7 +61,7 @@ export const ProviderTheming = (props: { emotionCache?: EmotionCache, children:
 
   return (
     <CacheProvider value={props.emotionCache || clientSideEmotionCache}>
-      <CssVarsProvider defaultMode='light' theme={theme}>
+      <CssVarsProvider defaultMode='system' theme={theme}>
         <CssBaseline />
         {/* Inject sprites to be referenced by SVG rendering */}
         <VendorIconSpriteMemo />