diff --git a/CHANGELOG.md b/CHANGELOG.md
index b414c179f0..600c120a45 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,10 @@
 
 ## Unreleased
 
+### Features
+
+- Add thread information to spans ([#4579](https://github.com/getsentry/sentry-react-native/pull/4579))
+
 ### Fixes
 
 - Considers the `SENTRY_DISABLE_AUTO_UPLOAD` and `SENTRY_DISABLE_NATIVE_DEBUG_UPLOAD` environment variables in the configuration of the Sentry Android Gradle Plugin for Expo plugin ([#4583](https://github.com/getsentry/sentry-react-native/pull/4583))
diff --git a/packages/core/src/js/tracing/integrations/appStart.ts b/packages/core/src/js/tracing/integrations/appStart.ts
index 0f96557d4c..572039f30e 100644
--- a/packages/core/src/js/tracing/integrations/appStart.ts
+++ b/packages/core/src/js/tracing/integrations/appStart.ts
@@ -1,4 +1,4 @@
-/* eslint-disable complexity */
+/* eslint-disable complexity, max-lines */
 import type { Client, Event, Integration, SpanJSON, TransactionEvent } from '@sentry/core';
 import {
   getCapturedScopesOnSpan,
@@ -26,6 +26,7 @@ import {
 } from '../ops';
 import { SPAN_ORIGIN_AUTO_APP_START, SPAN_ORIGIN_MANUAL_APP_START } from '../origin';
 import { SEMANTIC_ATTRIBUTE_SENTRY_OP } from '../semanticAttributes';
+import { setMainThreadInfo } from '../span';
 import { createChildSpanJSON, createSpanJSON, getBundleStartTimestampMs } from '../utils';
 
 const INTEGRATION_NAME = 'AppStart';
@@ -384,15 +385,17 @@ function createJSExecutionStartSpan(
 function convertNativeSpansToSpanJSON(parentSpan: SpanJSON, nativeSpans: NativeAppStartResponse['spans']): SpanJSON[] {
   return nativeSpans.map(span => {
     if (span.description === 'UIKit init') {
-      return createUIKitSpan(parentSpan, span);
+      return setMainThreadInfo(createUIKitSpan(parentSpan, span));
     }
 
-    return createChildSpanJSON(parentSpan, {
-      description: span.description,
-      start_timestamp: span.start_timestamp_ms / 1000,
-      timestamp: span.end_timestamp_ms / 1000,
-      origin: SPAN_ORIGIN_AUTO_APP_START,
-    });
+    return setMainThreadInfo(
+      createChildSpanJSON(parentSpan, {
+        description: span.description,
+        start_timestamp: span.start_timestamp_ms / 1000,
+        timestamp: span.end_timestamp_ms / 1000,
+        origin: SPAN_ORIGIN_AUTO_APP_START,
+      }),
+    );
   });
 }
 
diff --git a/packages/core/src/js/tracing/reactnativetracing.ts b/packages/core/src/js/tracing/reactnativetracing.ts
index d9ada0ff9d..30beeaec07 100644
--- a/packages/core/src/js/tracing/reactnativetracing.ts
+++ b/packages/core/src/js/tracing/reactnativetracing.ts
@@ -5,7 +5,7 @@ import { getClient } from '@sentry/core';
 
 import { isWeb } from '../utils/environment';
 import { getDevServer } from './../integrations/debugsymbolicatorutils';
-import { addDefaultOpForSpanFrom, defaultIdleOptions } from './span';
+import { addDefaultOpForSpanFrom, addThreadInfoToSpan, defaultIdleOptions } from './span';
 
 export const INTEGRATION_NAME = 'ReactNativeTracing';
 
@@ -119,6 +119,7 @@ export const reactNativeTracingIntegration = (
 
   const setup = (client: Client): void => {
     addDefaultOpForSpanFrom(client);
+    addThreadInfoToSpan(client);
 
     instrumentOutgoingRequests(client, {
       traceFetch: finalOptions.traceFetch,
diff --git a/packages/core/src/js/tracing/span.ts b/packages/core/src/js/tracing/span.ts
index b44425691c..d7909d8d6b 100644
--- a/packages/core/src/js/tracing/span.ts
+++ b/packages/core/src/js/tracing/span.ts
@@ -1,4 +1,4 @@
-import type { Client, Scope, Span, StartSpanOptions } from '@sentry/core';
+import type { Client, Scope, Span, SpanJSON, StartSpanOptions } from '@sentry/core';
 import {
   generatePropagationContext,
   getActiveSpan,
@@ -154,3 +154,28 @@ export function addDefaultOpForSpanFrom(client: Client): void {
     }
   });
 }
+
+export const SPAN_THREAD_NAME = 'thread.name';
+export const SPAN_THREAD_NAME_MAIN = 'main';
+export const SPAN_THREAD_NAME_JAVASCRIPT = 'javascript';
+
+/**
+ * Adds Javascript thread info to spans.
+ * Ref: https://reactnative.dev/architecture/threading-model
+ */
+export function addThreadInfoToSpan(client: Client): void {
+  client.on('spanStart', (span: Span) => {
+    if (!spanToJSON(span).data?.[SPAN_THREAD_NAME]) {
+      span.setAttribute(SPAN_THREAD_NAME, SPAN_THREAD_NAME_JAVASCRIPT);
+    }
+  });
+}
+
+/**
+ * Sets the Main thread info to the span.
+ */
+export function setMainThreadInfo(spanJSON: SpanJSON): SpanJSON {
+  spanJSON.data = spanJSON.data || {};
+  spanJSON.data[SPAN_THREAD_NAME] = SPAN_THREAD_NAME_MAIN;
+  return spanJSON;
+}
diff --git a/packages/core/test/tracing/integrations/appStart.test.ts b/packages/core/test/tracing/integrations/appStart.test.ts
index 4337e3e2b3..17709730dd 100644
--- a/packages/core/test/tracing/integrations/appStart.test.ts
+++ b/packages/core/test/tracing/integrations/appStart.test.ts
@@ -27,6 +27,7 @@ import {
   setRootComponentCreationTimestampMs,
 } from '../../../src/js/tracing/integrations/appStart';
 import { SPAN_ORIGIN_AUTO_APP_START, SPAN_ORIGIN_MANUAL_APP_START } from '../../../src/js/tracing/origin';
+import { SPAN_THREAD_NAME, SPAN_THREAD_NAME_MAIN } from '../../../src/js/tracing/span';
 import { getTimeOriginMilliseconds } from '../../../src/js/tracing/utils';
 import { RN_GLOBAL_OBJ } from '../../../src/js/utils/worldwide';
 import { NATIVE } from '../../../src/js/wrapper';
@@ -252,6 +253,7 @@ describe('App Start Integration', () => {
           data: {
             [SEMANTIC_ATTRIBUTE_SENTRY_OP]: appStartRootSpan!.op,
             [SEMANTIC_ATTRIBUTE_SENTRY_ORIGIN]: SPAN_ORIGIN_AUTO_APP_START,
+            [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_MAIN,
           },
         }),
       );
@@ -612,6 +614,7 @@ describe('App Start Integration', () => {
           data: {
             [SEMANTIC_ATTRIBUTE_SENTRY_OP]: appStartRootSpan!.op,
             [SEMANTIC_ATTRIBUTE_SENTRY_ORIGIN]: SPAN_ORIGIN_AUTO_APP_START,
+            [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_MAIN,
           },
         }),
       );
diff --git a/packages/core/test/tracing/reactnativenavigation.test.ts b/packages/core/test/tracing/reactnativenavigation.test.ts
index 09acbaa25f..ebc264d91f 100644
--- a/packages/core/test/tracing/reactnativenavigation.test.ts
+++ b/packages/core/test/tracing/reactnativenavigation.test.ts
@@ -32,6 +32,7 @@ import {
   SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE,
   SEMANTIC_ATTRIBUTE_SENTRY_SOURCE,
 } from '../../src/js/tracing/semanticAttributes';
+import { SPAN_THREAD_NAME, SPAN_THREAD_NAME_JAVASCRIPT } from '../../src/js/tracing/span';
 import { getDefaultTestClientOptions, TestClient } from '../mocks/client';
 
 interface MockEventsRegistry extends EventsRegistry {
@@ -87,6 +88,7 @@ describe('React Native Navigation Instrumentation', () => {
               [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
               [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
               [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+              [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
             },
           }),
         }),
@@ -131,6 +133,7 @@ describe('React Native Navigation Instrumentation', () => {
               [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
               [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
               [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+              [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
             },
           }),
         }),
@@ -206,6 +209,7 @@ describe('React Native Navigation Instrumentation', () => {
                 [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
                 [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
                 [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
             }),
           }),
@@ -294,6 +298,7 @@ describe('React Native Navigation Instrumentation', () => {
                 [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
                 [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
                 [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
             }),
           }),
@@ -342,6 +347,7 @@ describe('React Native Navigation Instrumentation', () => {
                 [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
                 [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
                 [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
             }),
           }),
diff --git a/packages/core/test/tracing/reactnavigation.test.ts b/packages/core/test/tracing/reactnavigation.test.ts
index 5c8b805e9d..e37c313c20 100644
--- a/packages/core/test/tracing/reactnavigation.test.ts
+++ b/packages/core/test/tracing/reactnavigation.test.ts
@@ -20,7 +20,7 @@ import {
   SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE,
   SEMANTIC_ATTRIBUTE_SENTRY_SOURCE,
 } from '../../src/js/tracing/semanticAttributes';
-import { DEFAULT_NAVIGATION_SPAN_NAME } from '../../src/js/tracing/span';
+import { DEFAULT_NAVIGATION_SPAN_NAME, SPAN_THREAD_NAME, SPAN_THREAD_NAME_JAVASCRIPT } from '../../src/js/tracing/span';
 import { RN_GLOBAL_OBJ } from '../../src/js/utils/worldwide';
 import { getDefaultTestClientOptions, TestClient } from '../mocks/client';
 import { NATIVE } from '../mockWrapper';
@@ -83,6 +83,7 @@ describe('ReactNavigationInstrumentation', () => {
               [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
               [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
               [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+              [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
             },
           }),
         }),
@@ -192,6 +193,7 @@ describe('ReactNavigationInstrumentation', () => {
               [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
               [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
               [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+              [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
             },
           }),
         }),
@@ -229,6 +231,7 @@ describe('ReactNavigationInstrumentation', () => {
               [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
               [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
               [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+              [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
             },
           }),
         }),
@@ -268,6 +271,7 @@ describe('ReactNavigationInstrumentation', () => {
               [SEMANTIC_ATTRIBUTE_SENTRY_OP]: 'navigation',
               [SEMANTIC_ATTRIBUTE_SENTRY_SAMPLE_RATE]: 1,
               [SEMANTIC_ATTRIBUTE_SENTRY_IDLE_SPAN_FINISH_REASON]: 'idleTimeout',
+              [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
             },
           }),
         }),
diff --git a/packages/core/test/tracing/reactnavigation.ttid.test.tsx b/packages/core/test/tracing/reactnavigation.ttid.test.tsx
index a0245cff12..c34c1271cb 100644
--- a/packages/core/test/tracing/reactnavigation.ttid.test.tsx
+++ b/packages/core/test/tracing/reactnavigation.ttid.test.tsx
@@ -16,6 +16,7 @@ import { startSpanManual } from '../../src/js';
 import { TimeToFullDisplay, TimeToInitialDisplay } from '../../src/js/tracing';
 import { _setAppStartEndTimestampMs } from '../../src/js/tracing/integrations/appStart';
 import { SPAN_ORIGIN_AUTO_NAVIGATION_REACT_NAVIGATION, SPAN_ORIGIN_AUTO_UI_TIME_TO_DISPLAY, SPAN_ORIGIN_MANUAL_UI_TIME_TO_DISPLAY } from '../../src/js/tracing/origin';
+import { SPAN_THREAD_NAME, SPAN_THREAD_NAME_JAVASCRIPT } from '../../src/js/tracing/span';
 import { isHermesEnabled, notWeb } from '../../src/js/utils/environment';
 import { createSentryFallbackEventEmitter } from '../../src/js/utils/sentryeventemitterfallback';
 import { RN_GLOBAL_OBJ } from '../../src/js/utils/worldwide';
@@ -80,6 +81,7 @@ describe('React Navigation - TTID', () => {
               data: {
                 'sentry.op': 'ui.load.initial_display',
                 'sentry.origin': SPAN_ORIGIN_AUTO_UI_TIME_TO_DISPLAY,
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
               description: 'New Screen initial display',
               op: 'ui.load.initial_display',
@@ -110,6 +112,7 @@ describe('React Navigation - TTID', () => {
               data: {
                 'sentry.op': 'ui.load.initial_display',
                 'sentry.origin': SPAN_ORIGIN_AUTO_UI_TIME_TO_DISPLAY,
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
               description: 'New Screen initial display',
               op: 'ui.load.initial_display',
@@ -146,6 +149,7 @@ describe('React Navigation - TTID', () => {
               data: {
                 'sentry.op': 'ui.load.initial_display',
                 'sentry.origin': SPAN_ORIGIN_AUTO_UI_TIME_TO_DISPLAY,
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
               description: 'New Screen initial display',
               op: 'ui.load.initial_display',
@@ -203,6 +207,7 @@ describe('React Navigation - TTID', () => {
                 'sentry.op': 'navigation.processing',
                 'sentry.origin': SPAN_ORIGIN_AUTO_NAVIGATION_REACT_NAVIGATION,
                 'sentry.source': 'custom',
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
               description: 'Navigation dispatch to screen New Screen mounted',
               op: 'navigation.processing',
@@ -231,6 +236,7 @@ describe('React Navigation - TTID', () => {
                 'sentry.op': 'navigation.processing',
                 'sentry.origin': SPAN_ORIGIN_AUTO_NAVIGATION_REACT_NAVIGATION,
                 'sentry.source': 'custom',
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
               description: 'Navigation dispatch to screen Initial Screen mounted',
               op: 'navigation.processing',
@@ -261,6 +267,7 @@ describe('React Navigation - TTID', () => {
               data: {
                 'sentry.op': 'ui.load.initial_display',
                 'sentry.origin': SPAN_ORIGIN_AUTO_UI_TIME_TO_DISPLAY,
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
               description: 'Initial Screen initial display',
               op: 'ui.load.initial_display',
@@ -295,6 +302,7 @@ describe('React Navigation - TTID', () => {
               data: {
                 'sentry.op': 'ui.load.full_display',
                 'sentry.origin': SPAN_ORIGIN_MANUAL_UI_TIME_TO_DISPLAY,
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
               description: 'Time To Full Display',
               op: 'ui.load.full_display',
@@ -371,6 +379,7 @@ describe('React Navigation - TTID', () => {
               data: {
                 'sentry.op': 'ui.load.initial_display',
                 'sentry.origin': SPAN_ORIGIN_AUTO_UI_TIME_TO_DISPLAY,
+                [SPAN_THREAD_NAME]: SPAN_THREAD_NAME_JAVASCRIPT,
               },
               description: 'New Screen initial display',
               op: 'ui.load.initial_display',