diff --git a/backend/app/services/tenant_service.py b/backend/app/services/tenant_service.py
new file mode 100644
index 0000000..f5eab09
--- /dev/null
+++ b/backend/app/services/tenant_service.py
@@ -0,0 +1,51 @@
+"""Tenant service: CRUD operations for tenants."""
+from sqlalchemy.orm import Session
+from typing import List, Optional
+from app.models.tenant import Tenant
+from app.schemas.tenant import TenantCreate, TenantUpdate, TenantResponse
+
+
+class TenantService:
+    @staticmethod
+    def list_tenants(db: Session, skip: int = 0, limit: int = 100) -> List[Tenant]:
+        return db.query(Tenant).offset(skip).limit(limit).all()
+
+    @staticmethod
+    def get_tenant(db: Session, tenant_id: int) -> Optional[Tenant]:
+        return db.query(Tenant).filter(Tenant.id == tenant_id).first()
+
+    @staticmethod
+    def create_tenant(db: Session, req: TenantCreate) -> Tenant:
+        # Check slug uniqueness
+        existing = db.query(Tenant).filter(Tenant.slug == req.slug).first()
+        if existing:
+            raise ValueError(f"Tenant slug '{req.slug}' already exists")
+        tenant = Tenant(
+            name=req.name,
+            slug=req.slug,
+            description=req.description,
+        )
+        db.add(tenant)
+        db.commit()
+        db.refresh(tenant)
+        return tenant
+
+    @staticmethod
+    def update_tenant(db: Session, tenant_id: int, req: TenantUpdate) -> Tenant:
+        tenant = db.query(Tenant).filter(Tenant.id == tenant_id).first()
+        if not tenant:
+            raise ValueError(f"Tenant #{tenant_id} not found")
+        for field, value in req.model_dump(exclude_unset=True).items():
+            setattr(tenant, field, value)
+        db.commit()
+        db.refresh(tenant)
+        return tenant
+
+    @staticmethod
+    def delete_tenant(db: Session, tenant_id: int) -> bool:
+        tenant = db.query(Tenant).filter(Tenant.id == tenant_id).first()
+        if not tenant:
+            return False
+        db.delete(tenant)
+        db.commit()
+        return True