diff --git a/packages/flutter/lib/src/material/radio.dart b/packages/flutter/lib/src/material/radio.dart
index 850a6815261..9a8e70e67b3 100644
--- a/packages/flutter/lib/src/material/radio.dart
+++ b/packages/flutter/lib/src/material/radio.dart
@@ -426,9 +426,11 @@ class Radio<T> extends StatefulWidget {
   ///  * [WidgetState.hovered].
   ///  * [WidgetState.focused].
   ///  * [WidgetState.disabled].
-  ///
-  /// If null, then it is transparent in all states.
   /// {@endtemplate}
+  ///
+  /// If null, then [RadioThemeData.backgroundColor] of [ThemeData.radioTheme]
+  /// is used. If that is also null the default value is transparent in all
+  /// states.
   final WidgetStateProperty<Color?>? backgroundColor;
 
   /// {@template flutter.material.Radio.side}
@@ -443,20 +445,23 @@ class Radio<T> extends StatefulWidget {
   ///  * [WidgetState.hovered].
   ///  * [WidgetState.focused].
   ///  * [WidgetState.disabled].
+  /// {@endtemplate}
   ///
   /// If null, then [RadioThemeData.side] of [ThemeData.radioTheme] is used. If
   /// that is also null, the default value is a border using the fill color.
-  /// {@endtemplate}
   final BorderSide? side;
 
+  /// {@template flutter.material.Radio.innerRadius}
   /// The radius of the inner circle of the radio button, in all [WidgetState]s.
   ///
   /// Resolves in the following states:
   ///  * [WidgetState.hovered].
   ///  * [WidgetState.focused].
   ///  * [WidgetState.disabled].
+  /// {@endtemplate}
   ///
-  /// If null, then it defaults to `4.5` in all states.
+  /// If null, then [RadioThemeData.innerRadius] of [ThemeData.radioTheme] is
+  /// used. If that is also null, the default value is `4.5` in all states.
   final WidgetStateProperty<double?>? innerRadius;
 
   @override
@@ -761,7 +766,10 @@ class _RadioPaintState extends State<_RadioPaint> {
           strokeAlign: BorderSide.strokeAlignCenter,
         );
 
-    final double innerRadius = widget.innerRadius?.resolve(activeStates) ?? _kInnerRadius;
+    final double innerRadius =
+        widget.innerRadius?.resolve(activeStates) ??
+        radioTheme.innerRadius?.resolve(activeStates) ??
+        _kInnerRadius;
 
     return CustomPaint(
       size: size,
diff --git a/packages/flutter/lib/src/material/radio_theme.dart b/packages/flutter/lib/src/material/radio_theme.dart
index 6278273c1f7..ffecfcaeb2c 100644
--- a/packages/flutter/lib/src/material/radio_theme.dart
+++ b/packages/flutter/lib/src/material/radio_theme.dart
@@ -51,6 +51,7 @@ class RadioThemeData with Diagnosticable {
     this.visualDensity,
     this.backgroundColor,
     this.side,
+    this.innerRadius,
   });
 
   /// {@macro flutter.widget.RawRadio.mouseCursor}
@@ -89,11 +90,23 @@ class RadioThemeData with Diagnosticable {
   final VisualDensity? visualDensity;
 
   /// {@macro flutter.material.Radio.backgroundColor}
+  ///
+  /// If specified, overrides the default value of [Radio.backgroundColor]. The
+  /// default value is transparent in all states.
   final WidgetStateProperty<Color?>? backgroundColor;
 
   /// {@macro flutter.material.Radio.side}
+  ///
+  /// If specified, overrides the default value of [Radio.side]. The default
+  /// value is a border using the fill color.
   final BorderSide? side;
 
+  /// {@macro flutter.material.Radio.innerRadius}
+  ///
+  /// If specified, overrides the default value of [Radio.innerRadius]. The
+  /// default value is `4.5` in all states.
+  final WidgetStateProperty<double?>? innerRadius;
+
   /// Creates a copy of this object but with the given fields replaced with the
   /// new values.
   RadioThemeData copyWith({
@@ -105,6 +118,7 @@ class RadioThemeData with Diagnosticable {
     VisualDensity? visualDensity,
     WidgetStateProperty<Color?>? backgroundColor,
     BorderSide? side,
+    WidgetStateProperty<double?>? innerRadius,
   }) {
     return RadioThemeData(
       mouseCursor: mouseCursor ?? this.mouseCursor,
@@ -115,6 +129,7 @@ class RadioThemeData with Diagnosticable {
       visualDensity: visualDensity ?? this.visualDensity,
       backgroundColor: backgroundColor ?? this.backgroundColor,
       side: side ?? this.side,
+      innerRadius: innerRadius ?? this.innerRadius,
     );
   }
 
@@ -144,9 +159,9 @@ class RadioThemeData with Diagnosticable {
     }
     return RadioThemeData(
       mouseCursor: t < 0.5 ? a?.mouseCursor : b?.mouseCursor,
-      fillColor: MaterialStateProperty.lerp<Color?>(a?.fillColor, b?.fillColor, t, Color.lerp),
+      fillColor: WidgetStateProperty.lerp<Color?>(a?.fillColor, b?.fillColor, t, Color.lerp),
       materialTapTargetSize: t < 0.5 ? a?.materialTapTargetSize : b?.materialTapTargetSize,
-      overlayColor: MaterialStateProperty.lerp<Color?>(
+      overlayColor: WidgetStateProperty.lerp<Color?>(
         a?.overlayColor,
         b?.overlayColor,
         t,
@@ -161,6 +176,7 @@ class RadioThemeData with Diagnosticable {
         Color.lerp,
       ),
       side: _lerpSides(a?.side, b?.side, t),
+      innerRadius: WidgetStateProperty.lerp<double?>(a?.innerRadius, b?.innerRadius, t, lerpDouble),
     );
   }
 
@@ -174,6 +190,7 @@ class RadioThemeData with Diagnosticable {
     visualDensity,
     backgroundColor,
     side,
+    innerRadius,
   );
 
   @override
@@ -192,28 +209,25 @@ class RadioThemeData with Diagnosticable {
         other.materialTapTargetSize == materialTapTargetSize &&
         other.visualDensity == visualDensity &&
         other.backgroundColor == backgroundColor &&
-        other.side == side;
+        other.side == side &&
+        other.innerRadius == innerRadius;
   }
 
   @override
   void debugFillProperties(DiagnosticPropertiesBuilder properties) {
     super.debugFillProperties(properties);
     properties.add(
-      DiagnosticsProperty<MaterialStateProperty<MouseCursor?>>(
+      DiagnosticsProperty<WidgetStateProperty<MouseCursor?>>(
         'mouseCursor',
         mouseCursor,
         defaultValue: null,
       ),
     );
     properties.add(
-      DiagnosticsProperty<MaterialStateProperty<Color?>>(
-        'fillColor',
-        fillColor,
-        defaultValue: null,
-      ),
+      DiagnosticsProperty<WidgetStateProperty<Color?>>('fillColor', fillColor, defaultValue: null),
     );
     properties.add(
-      DiagnosticsProperty<MaterialStateProperty<Color?>>(
+      DiagnosticsProperty<WidgetStateProperty<Color?>>(
         'overlayColor',
         overlayColor,
         defaultValue: null,
@@ -238,6 +252,13 @@ class RadioThemeData with Diagnosticable {
       ),
     );
     properties.add(DiagnosticsProperty<BorderSide>('side', side, defaultValue: null));
+    properties.add(
+      DiagnosticsProperty<WidgetStateProperty<double?>>(
+        'innerRadius',
+        innerRadius,
+        defaultValue: null,
+      ),
+    );
   }
 }
 
diff --git a/packages/flutter/test/material/radio_theme_test.dart b/packages/flutter/test/material/radio_theme_test.dart
index d52520d5e7d..a4af470f0cc 100644
--- a/packages/flutter/test/material/radio_theme_test.dart
+++ b/packages/flutter/test/material/radio_theme_test.dart
@@ -29,6 +29,7 @@ void main() {
     expect(themeData.visualDensity, null);
     expect(themeData.backgroundColor, null);
     expect(themeData.side, null);
+    expect(themeData.innerRadius, null);
 
     const RadioTheme theme = RadioTheme(data: RadioThemeData(), child: SizedBox());
     expect(theme.data.mouseCursor, null);
@@ -39,6 +40,7 @@ void main() {
     expect(theme.data.visualDensity, null);
     expect(theme.data.backgroundColor, null);
     expect(theme.data.side, null);
+    expect(theme.data.innerRadius, null);
   });
 
   testWidgets('Default RadioThemeData debugFillProperties', (WidgetTester tester) async {
@@ -64,6 +66,7 @@ void main() {
       visualDensity: VisualDensity.standard,
       backgroundColor: WidgetStatePropertyAll<Color>(Color(0xfffffff2)),
       side: BorderSide(color: Color(0xfffffff3), width: 2),
+      innerRadius: WidgetStatePropertyAll<double>(5.0),
     ).debugFillProperties(builder);
 
     final List<String> description = builder.properties
@@ -82,6 +85,7 @@ void main() {
         'visualDensity: VisualDensity#00000(h: 0.0, v: 0.0)',
         'backgroundColor: WidgetStatePropertyAll(${const Color(0xfffffff2)})',
         'side: BorderSide(color: ${const Color(0xfffffff3)}, width: 2.0)',
+        'innerRadius: WidgetStatePropertyAll(5.0)',
       ]),
     );
   });
@@ -99,6 +103,7 @@ void main() {
     const double splashRadius = 1.0;
     const MaterialTapTargetSize materialTapTargetSize = MaterialTapTargetSize.shrinkWrap;
     const VisualDensity visualDensity = VisualDensity(horizontal: 1, vertical: 1);
+    const double innerRadius = 5.0;
 
     Widget buildRadio({bool selected = false, bool autofocus = false}) {
       return MaterialApp(
@@ -129,6 +134,7 @@ void main() {
               }
               return defaultBackgroundColor;
             }),
+            innerRadius: const WidgetStatePropertyAll<double>(innerRadius),
           ),
         ),
         home: Scaffold(
@@ -161,7 +167,8 @@ void main() {
       _getRadioMaterial(tester),
       paints
         ..circle(color: selectedBackgroundColor)
-        ..circle(color: selectedFillColor),
+        ..circle(color: selectedFillColor)
+        ..circle(color: selectedFillColor, radius: innerRadius),
     );
 
     // Radio with hover.
@@ -243,6 +250,7 @@ void main() {
     const double themeSplashRadius = 1.0;
     const MaterialTapTargetSize themeMaterialTapTargetSize = MaterialTapTargetSize.padded;
     const VisualDensity themeVisualDensity = VisualDensity.standard;
+    const double themeInnerRadius = 5.0;
 
     const MouseCursor mouseCursor = SystemMouseCursors.text;
     const Color defaultFillColor = Color(0xeffffff0);
@@ -254,6 +262,7 @@ void main() {
     const double splashRadius = 2.0;
     const MaterialTapTargetSize materialTapTargetSize = MaterialTapTargetSize.shrinkWrap;
     const VisualDensity visualDensity = VisualDensity(horizontal: 1, vertical: 1);
+    const double innerRadius = 6.0;
 
     Widget buildRadio({bool selected = false, bool autofocus = false}) {
       return MaterialApp(
@@ -284,6 +293,7 @@ void main() {
               }
               return themeDefaultBackgroundColor;
             }),
+            innerRadius: const WidgetStatePropertyAll<double>(themeInnerRadius),
           ),
         ),
         home: Scaffold(
@@ -310,6 +320,7 @@ void main() {
               }
               return defaultBackgroundColor;
             }),
+            innerRadius: const WidgetStatePropertyAll<double>(innerRadius),
           ),
         ),
       );
@@ -334,7 +345,8 @@ void main() {
       _getRadioMaterial(tester),
       paints
         ..circle(color: selectedBackgroundColor)
-        ..circle(color: selectedFillColor),
+        ..circle(color: selectedFillColor)
+        ..circle(color: selectedFillColor, radius: innerRadius),
     );
 
     // Radio with hover.