diff --git a/packages/backend/migration/1732538997055-AddEnableAllowedEmailDomainOnly.js b/packages/backend/migration/1732538997055-AddEnableAllowedEmailDomainOnly.js
new file mode 100644
index 0000000000..4f30ac2dc8
--- /dev/null
+++ b/packages/backend/migration/1732538997055-AddEnableAllowedEmailDomainOnly.js
@@ -0,0 +1,16 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export class AddEnableAllowedEmailDomainOnly1732538997055 {
+    name = 'AddEnableAllowedEmailDomainOnly1732538997055'
+
+    async up(queryRunner) {
+        await queryRunner.query(`ALTER TABLE "meta" ADD "enableAllowedEmailDomainsOnly" boolean NOT NULL DEFAULT false`);
+    }
+
+    async down(queryRunner) {
+        await queryRunner.query(`ALTER TABLE "meta" DROP COLUMN "enableAllowedEmailDomainsOnly"`);
+    }
+}
diff --git a/packages/backend/src/core/EmailService.ts b/packages/backend/src/core/EmailService.ts
index 71d2c2c668..95a1290125 100644
--- a/packages/backend/src/core/EmailService.ts
+++ b/packages/backend/src/core/EmailService.ts
@@ -164,7 +164,7 @@ export class EmailService {
 	@bindThis
 	public async validateEmailForAccount(emailAddress: string): Promise<{
 		available: boolean;
-		reason: null | 'used' | 'format' | 'disposable' | 'mx' | 'smtp' | 'banned' | 'network' | 'blacklist';
+		reason: null | 'used' | 'format' | 'disposable' | 'mx' | 'smtp' | 'banned' | 'network' | 'blacklist' | 'allowedOnly';
 	}> {
 		const exist = await this.userProfilesRepository.countBy({
 			emailVerified: true,
@@ -188,6 +188,14 @@ export class EmailService {
 			};
 		}
 
+		// ホワイトリストのみ許可の場合は即座にfalseを返す
+		if (this.meta.enableAllowedEmailDomainsOnly) {
+			return {
+				available: false,
+				reason: 'allowedOnly',
+			};
+		}
+
 		const isBanned = this.utilityService.isBlockedHost(this.meta.bannedEmailDomains, emailDomain);
 
 		if (isBanned) {
diff --git a/packages/backend/src/models/Meta.ts b/packages/backend/src/models/Meta.ts
index 7966df0bcf..e386353497 100644
--- a/packages/backend/src/models/Meta.ts
+++ b/packages/backend/src/models/Meta.ts
@@ -581,6 +581,11 @@ export class MiMeta {
 	})
 	public enableAutoAddBannedEmailDomain: boolean;
 
+	@Column('boolean', {
+		default: false,
+	})
+	public enableAllowedEmailDomainsOnly: boolean;
+
 	@Column('varchar', {
 		length: 1024, array: true, default: '{ "admin", "administrator", "root", "system", "maintainer", "host", "mod", "moderator", "owner", "superuser", "staff", "auth", "i", "me", "everyone", "all", "mention", "mentions", "example", "user", "users", "account", "accounts", "official", "help", "helps", "support", "supports", "info", "information", "informations", "announce", "announces", "announcement", "announcements", "notice", "notification", "notifications", "dev", "developer", "developers", "tech", "misskey" }',
 	})
diff --git a/packages/backend/src/server/api/endpoints/admin/meta.ts b/packages/backend/src/server/api/endpoints/admin/meta.ts
index 4a6322f8f7..7429171a15 100644
--- a/packages/backend/src/server/api/endpoints/admin/meta.ts
+++ b/packages/backend/src/server/api/endpoints/admin/meta.ts
@@ -352,6 +352,10 @@ export const meta = {
 				type: 'boolean',
 				optional: false, nullable: false,
 			},
+			enableAllowedEmailDomainsOnly: {
+				type: 'boolean',
+				optional: false, nullable: false,
+			},
 			enableChartsForRemoteUser: {
 				type: 'boolean',
 				optional: false, nullable: false,
@@ -650,6 +654,7 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				truemailInstance: instance.truemailInstance,
 				truemailAuthKey: instance.truemailAuthKey,
 				enableAutoAddBannedEmailDomain: instance.enableAutoAddBannedEmailDomain,
+				enableAllowedEmailDomainsOnly: instance.enableAllowedEmailDomainsOnly,
 				enableChartsForRemoteUser: instance.enableChartsForRemoteUser,
 				enableChartsForFederatedInstances: instance.enableChartsForFederatedInstances,
 				enableStatsForFederatedInstances: instance.enableStatsForFederatedInstances,
diff --git a/packages/backend/src/server/api/endpoints/admin/update-meta.ts b/packages/backend/src/server/api/endpoints/admin/update-meta.ts
index cf6c46a33b..e54096b6d5 100644
--- a/packages/backend/src/server/api/endpoints/admin/update-meta.ts
+++ b/packages/backend/src/server/api/endpoints/admin/update-meta.ts
@@ -143,6 +143,7 @@ export const paramDef = {
 		bannedEmailDomains: { type: 'array', items: { type: 'string' } },
 		allowedEmailDomains: { type: 'array', items: { type: 'string' } },
 		enableAutoAddBannedEmailDomain: { type: 'boolean' },
+		enableAllowedEmailDomainsOnly: { type: 'boolean' },
 		preservedUsernames: { type: 'array', items: { type: 'string' } },
 		manifestJsonOverride: { type: 'string' },
 		enableFanoutTimeline: { type: 'boolean' },
@@ -649,6 +650,10 @@ export default class extends Endpoint<typeof meta, typeof paramDef> { // eslint-
 				set.enableAutoAddBannedEmailDomain = ps.enableAutoAddBannedEmailDomain;
 			}
 
+			if (ps.enableAllowedEmailDomainsOnly !== undefined) {
+				set.enableAllowedEmailDomainsOnly = ps.enableAllowedEmailDomainsOnly;
+			}
+
 			if (ps.urlPreviewEnabled !== undefined) {
 				set.urlPreviewEnabled = ps.urlPreviewEnabled;
 			}
diff --git a/packages/frontend/src/pages/admin/security.vue b/packages/frontend/src/pages/admin/security.vue
index b9cf7a4578..182b77f260 100644
--- a/packages/frontend/src/pages/admin/security.vue
+++ b/packages/frontend/src/pages/admin/security.vue
@@ -101,6 +101,10 @@ SPDX-License-Identifier: AGPL-3.0-only
 					<MkTextarea v-model="allowedEmailDomainsForm.state.allowedEmailDomains">
 						<template #label>Allowed Email Domains List</template>
 					</MkTextarea>
+
+					<MkSwitch v-model="allowedEmailDomainsForm.state.enableAllowedEmailDomainsOnly">
+						<template #label>Enable Allowed Email Domains Only</template>
+					</MkSwitch>
 				</div>
 			</MkFolder>
 
@@ -213,9 +217,11 @@ const emailValidationForm = useForm({
 
 const allowedEmailDomainsForm = useForm({
 	allowedEmailDomains: meta.allowedEmailDomains?.join('\n') || '',
+	enableAllowedEmailDomainsOnly: meta.enableAllowedEmailDomainsOnly,
 }, async (state) => {
 	await os.apiWithDialog('admin/update-meta', {
 		allowedEmailDomains: state.allowedEmailDomains.split('\n'),
+		enableAllowedEmailDomainsOnly: state.enableAllowedEmailDomainsOnly,
 	});
 	fetchInstance(true);
 });
diff --git a/packages/misskey-js/src/autogen/types.ts b/packages/misskey-js/src/autogen/types.ts
index 06dea39fc3..12b9ffb573 100644
--- a/packages/misskey-js/src/autogen/types.ts
+++ b/packages/misskey-js/src/autogen/types.ts
@@ -5177,6 +5177,7 @@ export type operations = {
             truemailInstance: string | null;
             truemailAuthKey: string | null;
             enableAutoAddBannedEmailDomain: boolean;
+            enableAllowedEmailDomainsOnly: boolean;
             enableChartsForRemoteUser: boolean;
             enableChartsForFederatedInstances: boolean;
             enableStatsForFederatedInstances: boolean;
@@ -9582,6 +9583,7 @@ export type operations = {
           bannedEmailDomains?: string[];
           allowedEmailDomains?: string[];
           enableAutoAddBannedEmailDomain?: boolean;
+          enableAllowedEmailDomainsOnly?: boolean;
           preservedUsernames?: string[];
           manifestJsonOverride?: string;
           enableFanoutTimeline?: boolean;