diff --git a/.config/docker_example.yml b/.config/docker_example.yml
index 2ec6cf8734..59a0ff7187 100644
--- a/.config/docker_example.yml
+++ b/.config/docker_example.yml
@@ -56,17 +56,17 @@ dbReplications: false
 # You can configure any number of replicas here
 #dbSlaves:
 #  -
-#    host: 
-#    port: 
-#    db: 
-#    user: 
-#    pass: 
+#    host:
+#    port:
+#    db:
+#    user:
+#    pass:
 #  -
-#    host: 
-#    port: 
-#    db: 
-#    user: 
-#    pass: 
+#    host:
+#    port:
+#    db:
+#    user:
+#    pass:
 
 #   ┌─────────────────────┐
 #───┘ Redis configuration └─────────────────────────────────────
@@ -154,6 +154,9 @@ id: 'aidx'
 #  saKeyPath: /path/to/service-account-key.json
 #  logName: cherrypick
 
+# Override the file URL rendering in ActivityPub (Object Storage file only)
+#apFileBaseUrl: https://example.com/
+
 # Proxy for HTTP/HTTPS
 #proxy: http://127.0.0.1:3128
 
diff --git a/.config/example.yml b/.config/example.yml
index a74996e463..b38756d1fa 100644
--- a/.config/example.yml
+++ b/.config/example.yml
@@ -172,6 +172,9 @@ id: 'aidx'
 #  saKeyPath: /path/to/service-account-key.json
 #  logName: cherrypick
 
+# Override the file URL rendering in ActivityPub (Object Storage file only)
+#apFileBaseUrl: https://example.com/
+
 # Proxy for HTTP/HTTPS
 #proxy: http://127.0.0.1:3128
 
diff --git a/.devcontainer/devcontainer.yml b/.devcontainer/devcontainer.yml
index 741f768cf0..5f9b66a40d 100644
--- a/.devcontainer/devcontainer.yml
+++ b/.devcontainer/devcontainer.yml
@@ -56,17 +56,17 @@ dbReplications: false
 # You can configure any number of replicas here
 #dbSlaves:
 #  -
-#    host: 
-#    port: 
-#    db: 
-#    user: 
-#    pass: 
+#    host:
+#    port:
+#    db:
+#    user:
+#    pass:
 #  -
-#    host: 
-#    port: 
-#    db: 
-#    user: 
-#    pass: 
+#    host:
+#    port:
+#    db:
+#    user:
+#    pass:
 
 #   ┌─────────────────────┐
 #───┘ Redis configuration └─────────────────────────────────────
@@ -154,6 +154,9 @@ id: 'aidx'
 #  saKeyPath: /path/to/service-account-key.json
 #  logName: cherrypick
 
+# Override the file URL rendering in ActivityPub (Object Storage file only)
+#apFileBaseUrl: https://example.com/
+
 # Proxy for HTTP/HTTPS
 #proxy: http://127.0.0.1:3128
 
diff --git a/chart/files/default.yml b/chart/files/default.yml
index f209e90a31..178d87026e 100644
--- a/chart/files/default.yml
+++ b/chart/files/default.yml
@@ -77,17 +77,17 @@ dbReplications: false
 # You can configure any number of replicas here
 #dbSlaves:
 #  -
-#    host: 
-#    port: 
-#    db: 
-#    user: 
-#    pass: 
+#    host:
+#    port:
+#    db:
+#    user:
+#    pass:
 #  -
-#    host: 
-#    port: 
-#    db: 
-#    user: 
-#    pass: 
+#    host:
+#    port:
+#    db:
+#    user:
+#    pass:
 
 #   ┌─────────────────────┐
 #───┘ Redis configuration └─────────────────────────────────────
@@ -174,6 +174,9 @@ id: "aidx"
 #  saKeyPath: /path/to/service-account-key.json
 #  logName: cherrypick
 
+# Override the file URL rendering in ActivityPub (Object Storage file only)
+#apFileBaseUrl: https://example.com/
+
 # Proxy for HTTP/HTTPS
 #proxy: http://127.0.0.1:3128
 
diff --git a/packages/backend/src/config.ts b/packages/backend/src/config.ts
index 0798fd1914..ccf7e18f23 100644
--- a/packages/backend/src/config.ts
+++ b/packages/backend/src/config.ts
@@ -86,6 +86,8 @@ type Source = {
 		logName?: string;
 	}
 
+	apFileBaseUrl?: string;
+
 	mediaProxy?: string;
 	proxyRemoteFiles?: boolean;
 	videoThumbnailGenerator?: string;
@@ -145,6 +147,7 @@ export type Config = {
 	relashionshipJobPerSec: number | undefined;
 	deliverJobMaxAttempts: number | undefined;
 	inboxJobMaxAttempts: number | undefined;
+	apFileBaseUrl: string | undefined;
 	proxyRemoteFiles: boolean | undefined;
 	signToActivityPubGet: boolean | undefined;
 
@@ -250,6 +253,7 @@ export function loadConfig(): Config {
 		inboxJobMaxAttempts: config.inboxJobMaxAttempts,
 		proxyRemoteFiles: config.proxyRemoteFiles,
 		signToActivityPubGet: config.signToActivityPubGet,
+		apFileBaseUrl: config.apFileBaseUrl,
 		mediaProxy: externalMediaProxy ?? internalMediaProxy,
 		externalMediaProxyEnabled: externalMediaProxy !== null && externalMediaProxy !== internalMediaProxy,
 		videoThumbnailGenerator: config.videoThumbnailGenerator ?
diff --git a/packages/backend/src/core/activitypub/ApRendererService.ts b/packages/backend/src/core/activitypub/ApRendererService.ts
index c967439c12..8e0ae86cb5 100644
--- a/packages/backend/src/core/activitypub/ApRendererService.ts
+++ b/packages/backend/src/core/activitypub/ApRendererService.ts
@@ -166,7 +166,7 @@ export class ApRendererService {
 		return {
 			type: 'Document',
 			mediaType: file.webpublicType ?? file.type,
-			url: this.driveFileEntityService.getPublicUrl(file),
+			url: this.driveFileEntityService.getPublicUrl(file, undefined, true),
 			name: file.comment,
 		};
 	}
@@ -245,7 +245,7 @@ export class ApRendererService {
 	public renderImage(file: MiDriveFile): IApImage {
 		return {
 			type: 'Image',
-			url: this.driveFileEntityService.getPublicUrl(file),
+			url: this.driveFileEntityService.getPublicUrl(file, undefined, true),
 			sensitive: file.isSensitive,
 			name: file.comment,
 		};
diff --git a/packages/backend/src/core/activitypub/models/ApPersonService.ts b/packages/backend/src/core/activitypub/models/ApPersonService.ts
index 679715f239..52d110f840 100644
--- a/packages/backend/src/core/activitypub/models/ApPersonService.ts
+++ b/packages/backend/src/core/activitypub/models/ApPersonService.ts
@@ -250,8 +250,8 @@ export class ApPersonService implements OnModuleInit {
 		return {
 			avatarId: avatar?.id ?? null,
 			bannerId: banner?.id ?? null,
-			avatarUrl: avatar ? this.driveFileEntityService.getPublicUrl(avatar, 'avatar') : null,
-			bannerUrl: banner ? this.driveFileEntityService.getPublicUrl(banner) : null,
+			avatarUrl: avatar ? this.driveFileEntityService.getPublicUrl(avatar, 'avatar', true) : null,
+			bannerUrl: banner ? this.driveFileEntityService.getPublicUrl(banner, undefined, true) : null,
 			avatarBlurhash: avatar?.blurhash ?? null,
 			bannerBlurhash: banner?.blurhash ?? null,
 		};
diff --git a/packages/backend/src/core/entities/DriveFileEntityService.ts b/packages/backend/src/core/entities/DriveFileEntityService.ts
index 837a7ab13d..c3ad6746cd 100644
--- a/packages/backend/src/core/entities/DriveFileEntityService.ts
+++ b/packages/backend/src/core/entities/DriveFileEntityService.ts
@@ -107,7 +107,7 @@ export class DriveFileEntityService {
 	}
 
 	@bindThis
-	public getPublicUrl(file: MiDriveFile, mode?: 'avatar'): string { // static = thumbnail
+	public getPublicUrl(file: MiDriveFile, mode?: 'avatar', ap?: boolean): string { // static = thumbnail
 		// リモートかつメディアプロキシ
 		if (file.uri != null && file.userHost != null && this.config.externalMediaProxyEnabled) {
 			return this.getProxiedUrl(file.uri, mode);
@@ -129,6 +129,16 @@ export class DriveFileEntityService {
 		if (mode === 'avatar') {
 			return this.getProxiedUrl(url, 'avatar');
 		}
+
+		if (ap && this.config.apFileBaseUrl) {
+			const baseUrl = this.config.apFileBaseUrl;
+			const isValidBaseUrl = /^https?:\/\/[\w.-]+\.[a-zA-Z]{2,}(\/.*)?$/i.test(baseUrl);
+			if (isValidBaseUrl) {
+				const trimmedBaseUrl = baseUrl.replace(/\/$/, '');
+				return url.replace(/^https?:\/\/[\w.-]+\.[a-zA-Z]{2,}/, trimmedBaseUrl);
+			}
+		}
+
 		return url;
 	}