diff --git a/README.md b/README.md
index ff371c6..2b70c06 100644
--- a/README.md
+++ b/README.md
@@ -352,6 +352,41 @@ Rules of thumb:
 | `EventCategory.marketing` | Campaign attribution, ad interactions |
 | `EventCategory.system` | App lifecycle, background tasks |
 
+### Custom categories
+
+If the predefined categories don't fit your domain, define your own with `defineCategory()` on the `RoutingBuilder`:
+
+```dart
+FlexTrack.configure(
+  RoutingBuilder()
+    .defineCategory('experiments', description: 'A/B test and feature flag events')
+    .defineCategory('payments', description: 'Payment flow events')
+    // ... rest of your config
+);
+```
+
+Then assign it in your event:
+
+```dart
+class ExperimentEvent extends TrackableEvent {
+  @override
+  EventCategory get category => const EventCategory('experiments');
+}
+```
+
+And route it like any predefined category:
+
+```dart
+.routeCategory(const EventCategory('experiments')).to(['analytics']).and()
+```
+
+You can also create a subcategory of an existing one:
+
+```dart
+final paymentsCategory = EventCategory.business.createSubcategory('payments');
+// results in name: 'business_payments'
+```
+
 ---
 
 ## Creating trackers
diff --git a/test/routing/routing_engine_test.dart b/test/routing/routing_engine_test.dart
index 0bb1362..878991b 100644
--- a/test/routing/routing_engine_test.dart
+++ b/test/routing/routing_engine_test.dart
@@ -1054,6 +1054,129 @@ void main() {
       });
     });
 
+    group('Custom Category Routing', () {
+      test('should route event with custom category to correct tracker', () {
+        const experimentsCategory = EventCategory('experiments');
+        config = RoutingConfiguration(
+          rules: [
+            RoutingRule(
+              category: experimentsCategory,
+              targetGroup: TrackerGroup('experiments', ['ab_tracker']),
+              priority: 10,
+            ),
+            RoutingRule(
+              isDefault: true,
+              targetGroup: TrackerGroup('default', ['analytics']),
+            ),
+          ],
+          customCategories: {'experiments': experimentsCategory},
+        );
+        engine = RoutingEngine(config);
+
+        final result = engine.routeEvent(
+          CustomCategoryTestEvent('experiment_viewed', experimentsCategory),
+          availableTrackers: {'ab_tracker', 'analytics'},
+        );
+
+        expect(result.targetTrackers, contains('ab_tracker'));
+        expect(result.targetTrackers, isNot(contains('analytics')));
+        expect(result.appliedRules.first.category, equals(experimentsCategory));
+      });
+
+      test('should fall through to default when custom category does not match',
+          () {
+        const experimentsCategory = EventCategory('experiments');
+        const paymentsCategory = EventCategory('payments');
+        config = RoutingConfiguration(
+          rules: [
+            RoutingRule(
+              category: experimentsCategory,
+              targetGroup: TrackerGroup('experiments', ['ab_tracker']),
+              priority: 10,
+            ),
+            RoutingRule(
+              isDefault: true,
+              targetGroup: TrackerGroup('default', ['analytics']),
+            ),
+          ],
+          customCategories: {
+            'experiments': experimentsCategory,
+            'payments': paymentsCategory,
+          },
+        );
+        engine = RoutingEngine(config);
+
+        final result = engine.routeEvent(
+          CustomCategoryTestEvent('payment_completed', paymentsCategory),
+          availableTrackers: {'ab_tracker', 'analytics'},
+        );
+
+        expect(result.targetTrackers, contains('analytics'));
+        expect(result.targetTrackers, isNot(contains('ab_tracker')));
+        expect(result.appliedRules.first.isDefault, isTrue);
+      });
+
+      test('should route subcategory event using full subcategory name', () {
+        final paymentsSubcategory =
+            EventCategory.business.createSubcategory('payments');
+        config = RoutingConfiguration(
+          rules: [
+            RoutingRule(
+              category: paymentsSubcategory,
+              targetGroup: TrackerGroup('payments', ['payment_tracker']),
+              priority: 15,
+            ),
+            RoutingRule(
+              category: EventCategory.business,
+              targetGroup: TrackerGroup('business', ['analytics']),
+              priority: 10,
+            ),
+            RoutingRule(
+              isDefault: true,
+              targetGroup: TrackerGroup('default', ['default_tracker']),
+            ),
+          ],
+          customCategories: {'business_payments': paymentsSubcategory},
+        );
+        engine = RoutingEngine(config);
+
+        final subcategoryResult = engine.routeEvent(
+          CustomCategoryTestEvent('checkout_completed', paymentsSubcategory),
+          availableTrackers: {'payment_tracker', 'analytics', 'default_tracker'},
+        );
+
+        expect(subcategoryResult.targetTrackers, contains('payment_tracker'));
+        expect(subcategoryResult.targetTrackers, isNot(contains('analytics')));
+      });
+
+      test('should treat two EventCategory instances with same name as equal',
+          () {
+        config = RoutingConfiguration(
+          rules: [
+            RoutingRule(
+              category: const EventCategory('experiments'),
+              targetGroup: TrackerGroup('experiments', ['ab_tracker']),
+              priority: 10,
+            ),
+            RoutingRule(
+              isDefault: true,
+              targetGroup: TrackerGroup('default', ['analytics']),
+            ),
+          ],
+        );
+        engine = RoutingEngine(config);
+
+        // Different instance, same name — equality is name-based
+        final result = engine.routeEvent(
+          CustomCategoryTestEvent(
+              'flag_exposed', const EventCategory('experiments')),
+          availableTrackers: {'ab_tracker', 'analytics'},
+        );
+
+        expect(result.targetTrackers, contains('ab_tracker'));
+      });
+    });
+
     group('Edge Cases and Error Handling', () {
       test('should handle empty available trackers', () {
         config = RoutingConfiguration(
@@ -1425,3 +1548,19 @@ class PropertyTestEvent extends BaseEvent {
   @override
   bool get containsPII => mockContainsPII;
 }
+
+class CustomCategoryTestEvent extends BaseEvent {
+  final String eventName;
+  final EventCategory _category;
+
+  CustomCategoryTestEvent(this.eventName, this._category);
+
+  @override
+  String getName() => eventName;
+
+  @override
+  Map<String, Object>? getProperties() => null;
+
+  @override
+  EventCategory get category => _category;
+}