diff --git a/apps/operator/pages/tenants/[slug].vue b/apps/operator/pages/tenants/[slug].vue
index 29c9ec9..8fc710f 100644
--- a/apps/operator/pages/tenants/[slug].vue
+++ b/apps/operator/pages/tenants/[slug].vue
@@ -82,7 +82,7 @@ const INTEGRATIONS = ['authentik', 'stalwart', 'ocis'] as const
 type IntegrationKey = (typeof INTEGRATIONS)[number]
 
 // ── Danger-zone state ─────────────────────────────────────────────────────
-const dangerAction = ref<'suspend' | 'resume' | 'delete' | null>(null)
+const dangerAction = ref<'suspend' | 'resume' | 'delete' | 'purge' | null>(null)
 const dangerBusy = ref(false)
 const dangerError = ref<string | null>(null)
 const reconcileBusy = ref(false)
@@ -99,6 +99,11 @@ async function confirmDanger() {
       await $fetch(`/api/tenants/${slug.value}/resume`, { method: 'POST' })
     } else if (dangerAction.value === 'delete') {
       await $fetch(`/api/tenants/${slug.value}`, { method: 'DELETE' })
+    } else if (dangerAction.value === 'purge') {
+      await $fetch(`/api/tenants/${slug.value}/purge`, { method: 'DELETE' })
+      // The tenant no longer exists — back to the list.
+      await navigateTo('/tenants')
+      return
     }
     await refreshTenant()
     dangerAction.value = null
@@ -343,14 +348,27 @@ async function reconcile() {
             @click="dangerAction = 'delete'; dangerError = null"
           >Soft-delete tenant</UiButton>
         </Card>
+
+        <Card v-if="tenant.status === 'deleted'">
+          <h2 class="danger">Purge permanently</h2>
+          <p>
+            Tears down external resources (Stalwart domains, Authentik group) and removes
+            every Mongo record except the audit trail. Frees the slug for reuse.
+            Irreversible.
+          </p>
+          <UiButton
+            variant="danger"
+            @click="dangerAction = 'purge'; dangerError = null"
+          >Purge tenant</UiButton>
+        </Card>
       </div>
     </div>
 
     <ConfirmDialog
       :open="dangerAction !== null"
       :eyebrow="`Tenant · ${tenant.slug}`"
-      :title="dangerAction === 'delete' ? 'Soft-delete this tenant?' : dangerAction === 'suspend' ? 'Suspend this tenant?' : 'Resume this tenant?'"
-      :confirm-label="dangerAction === 'delete' ? 'Delete' : dangerAction === 'suspend' ? 'Suspend' : 'Resume'"
+      :title="dangerAction === 'purge' ? 'Purge this tenant permanently?' : dangerAction === 'delete' ? 'Soft-delete this tenant?' : dangerAction === 'suspend' ? 'Suspend this tenant?' : 'Resume this tenant?'"
+      :confirm-label="dangerAction === 'purge' ? 'Purge forever' : dangerAction === 'delete' ? 'Delete' : dangerAction === 'suspend' ? 'Suspend' : 'Resume'"
       :tone="dangerAction === 'resume' ? 'primary' : 'danger'"
       :busy="dangerBusy"
       @close="dangerAction = null"
@@ -363,6 +381,11 @@ async function reconcile() {
       <p v-else-if="dangerAction === 'resume'">
         Lift the suspension on <strong>{{ tenant.name }}</strong>. Logins resume immediately.
       </p>
+      <p v-else-if="dangerAction === 'purge'">
+        Permanently erase <strong>{{ tenant.name }}</strong>: Stalwart domains and the
+        Authentik group are deleted, and all records except the audit trail are removed.
+        This cannot be undone.
+      </p>
       <p v-else>
         Mark <strong>{{ tenant.name }}</strong> as deleted. Their data stays in Mongo until
         the cleanup job runs; external resources stay untouched.
diff --git a/apps/operator/server/api/tenants/[slug]/purge.delete.ts b/apps/operator/server/api/tenants/[slug]/purge.delete.ts
new file mode 100644
index 0000000..356c806
--- /dev/null
+++ b/apps/operator/server/api/tenants/[slug]/purge.delete.ts
@@ -0,0 +1,6 @@
+import { platformApi } from '~~/server/utils/platform-api'
+
+export default defineEventHandler(async (event) => {
+  const slug = getRouterParam(event, 'slug')
+  return platformApi(event, `/tenants/${slug}/purge`, { method: 'DELETE' })
+})
diff --git a/services/platform-api/src/tenants/tenants.controller.ts b/services/platform-api/src/tenants/tenants.controller.ts
index df9ec6a..99443cc 100644
--- a/services/platform-api/src/tenants/tenants.controller.ts
+++ b/services/platform-api/src/tenants/tenants.controller.ts
@@ -292,6 +292,19 @@ export class TenantsController {
     await this.tenants.softDelete(slug, auditActor(user, req))
   }
 
+  // Hard delete. Only valid on an already soft-deleted tenant (two-step on
+  // purpose) — tears down external resources and removes every Mongo trace
+  // except the audit log, freeing the slug for reuse.
+  @Delete(':slug/purge')
+  @HttpCode(204)
+  async purge(@Param('slug') slug: string, @CurrentUser() jwt: AuthentikJwtPayload, @Req() req: Parameters<typeof clientIp>[0]) {
+    const user = await this.actor.resolve(jwt)
+    if (!user.platformAdmin) {
+      throw new ForbiddenException('Only platform admins can purge tenants')
+    }
+    await this.tenants.purge(slug, auditActor(user, req))
+  }
+
   // Manually re-run provisioning. Useful when an integration was down at create
   // time, or when external state drifted (someone deleted the Authentik group
   // out of band). Idempotent — already-OK steps no-op.
diff --git a/services/platform-api/src/tenants/tenants.module.ts b/services/platform-api/src/tenants/tenants.module.ts
index 182b3db..a5295bf 100644
--- a/services/platform-api/src/tenants/tenants.module.ts
+++ b/services/platform-api/src/tenants/tenants.module.ts
@@ -4,6 +4,8 @@ import { AuditModule } from '../audit/audit.module.js'
 import { AuthModule } from '../auth/auth.module.js'
 import { IntegrationsModule } from '../integrations/integrations.module.js'
 import { PricesModule } from '../prices/prices.module.js'
+import { Domain, DomainSchema } from '../schemas/domain.schema.js'
+import { Invoice, InvoiceSchema } from '../schemas/invoice.schema.js'
 import { Subscription, SubscriptionSchema } from '../schemas/subscription.schema.js'
 import { TenantBranding, TenantBrandingSchema } from '../schemas/tenant-branding.schema.js'
 import { TenantSsoApp, TenantSsoAppSchema } from '../schemas/tenant-sso-app.schema.js'
@@ -26,6 +28,9 @@ import { TenantsService } from './tenants.service.js'
       // lookup goes through PricesService for the soft-active filter.
       { name: Subscription.name, schema: SubscriptionSchema },
       { name: TenantBranding.name, schema: TenantBrandingSchema },
+      // Domain + Invoice are only touched by purge() — the hard-delete cascade.
+      { name: Domain.name, schema: DomainSchema },
+      { name: Invoice.name, schema: InvoiceSchema },
       { name: TenantSsoApp.name, schema: TenantSsoAppSchema },
     ]),
     AuthModule,
diff --git a/services/platform-api/src/tenants/tenants.service.ts b/services/platform-api/src/tenants/tenants.service.ts
index f65be0d..e297b82 100644
--- a/services/platform-api/src/tenants/tenants.service.ts
+++ b/services/platform-api/src/tenants/tenants.service.ts
@@ -9,9 +9,12 @@ import { InjectModel } from '@nestjs/mongoose'
 import { Model, Types } from 'mongoose'
 import { AuditService, type AuditActor } from '../audit/audit.service.js'
 import { AuthentikClient } from '../integrations/authentik.client.js'
+import { StalwartClient } from '../integrations/stalwart.client.js'
 import { StripeClient } from '../integrations/stripe.client.js'
 import { PricesService } from '../prices/prices.service.js'
 import type { PriceCurrency, PriceCycle, PriceDocument } from '../schemas/price.schema.js'
+import { Domain, DomainDocument } from '../schemas/domain.schema.js'
+import { Invoice, InvoiceDocument } from '../schemas/invoice.schema.js'
 import { Subscription, SubscriptionDocument } from '../schemas/subscription.schema.js'
 import { Tenant, TenantDocument } from '../schemas/tenant.schema.js'
 import { User, UserDocument, roleForTenant } from '../schemas/user.schema.js'
@@ -30,11 +33,14 @@ export class TenantsService {
     @InjectModel(Tenant.name) private readonly tenantModel: Model<TenantDocument>,
     @InjectModel(User.name) private readonly userModel: Model<UserDocument>,
     @InjectModel(Subscription.name) private readonly subModel: Model<SubscriptionDocument>,
+    @InjectModel(Domain.name) private readonly domainModel: Model<DomainDocument>,
+    @InjectModel(Invoice.name) private readonly invoiceModel: Model<InvoiceDocument>,
     private readonly provisioning: ProvisioningService,
     private readonly audit: AuditService,
     private readonly prices: PricesService,
     private readonly stripe: StripeClient,
     private readonly authentik: AuthentikClient,
+    private readonly stalwart: StalwartClient,
   ) {}
 
   async listUsersForTenant(slug: string): Promise<UserDocument[]> {
@@ -379,6 +385,62 @@ export class TenantsService {
     )
   }
 
+  // Permanently remove a soft-deleted tenant: best-effort external teardown
+  // (Stalwart service + customer domains, Authentik group), then the Mongo
+  // cascade (domains, subscriptions, invoices, user links, the tenant doc).
+  // Two-step by design — purge refuses tenants that aren't already
+  // soft-deleted, so a stray click can never erase a live customer.
+  async purge(slug: string, actor?: AuditActor): Promise<void> {
+    const tenant = await this.findOneBySlug(slug)
+    if (tenant.status !== 'deleted') {
+      throw new ConflictException(`Tenant "${slug}" must be soft-deleted before it can be purged`)
+    }
+
+    // External teardown is best-effort: a dead integration must not leave the
+    // tenant stuck half-purged — leftovers are visible in the integrations'
+    // own admin UIs and are idempotent to remove later.
+    const warn = (what: string) => (err: unknown) =>
+      this.logger.warn(`purge(${slug}): ${what} teardown failed: ${(err as Error).message}`)
+    if (tenant.stalwartDomain) {
+      await this.stalwart.deleteDomain(tenant.stalwartDomain).catch(warn('stalwart service domain'))
+    }
+    const platformBase = (process.env.PLATFORM_TENANT_DOMAIN || 'dezky.local').toLowerCase()
+    const domains = await this.domainModel.find({ tenantId: tenant._id }).exec()
+    for (const d of domains) {
+      // Never drop the platform apex from Stalwart — the management admin
+      // account lives in that domain.
+      if (d.stalwartProvisioned && d.domain !== platformBase) {
+        await this.stalwart.deleteDomain(d.domain).catch(warn(`stalwart domain ${d.domain}`))
+      }
+    }
+    if (tenant.authentikGroupId) {
+      await this.authentik.deleteGroup(tenant.authentikGroupId).catch(warn('authentik group'))
+    }
+
+    await this.domainModel.deleteMany({ tenantId: tenant._id }).exec()
+    await this.subModel.deleteMany({ tenantId: tenant._id }).exec()
+    await this.invoiceModel.deleteMany({ tenantId: tenant._id }).exec()
+    await this.userModel
+      .updateMany(
+        { tenantIds: tenant._id },
+        { $pull: { tenantIds: tenant._id }, $unset: { [`tenantRoles.${String(tenant._id)}`]: '' } },
+      )
+      .exec()
+    await this.tenantModel.deleteOne({ _id: tenant._id }).exec()
+
+    void this.audit.record(
+      {
+        action: 'tenant.purged',
+        resourceType: 'tenant',
+        resourceId: String(tenant._id),
+        resourceName: tenant.name,
+        tenantSlug: tenant.slug,
+        metadata: { stalwartDomain: tenant.stalwartDomain, customerDomains: domains.map((d) => d.domain) },
+      },
+      actor,
+    )
+  }
+
   async setStatus(
     slug: string,
     status: 'active' | 'suspended',