diff --git a/prisma/seed.ts b/prisma/seed.ts
index 90313c7..13b6dc4 100644
--- a/prisma/seed.ts
+++ b/prisma/seed.ts
@@ -82,8 +82,51 @@ async function main() {
 
   console.log(`Super-admin upserted: ${superAdmin.email} (${superAdmin.id})`);
 
+  // -----------------------------------------------------------------------
+  // Tenant: Test ISP 2 (for cross-tenant isolation testing)
+  // -----------------------------------------------------------------------
+  const demoTenant2 = await prisma.tenant.upsert({
+    where: { slug: "test-isp-2" },
+    update: {},
+    create: {
+      name: "Test ISP 2",
+      slug: "test-isp-2",
+      ownerEmail: "admin2@demo.com",
+      status: TenantStatus.ACTIVE,
+    },
+  });
+
+  console.log(`Tenant upserted: ${demoTenant2.name} (${demoTenant2.id})`);
+
+  // -----------------------------------------------------------------------
+  // Admin user: admin2@demo.com / admin123
+  // Scoped to Test ISP 2 tenant (for cross-tenant isolation tests)
+  // -----------------------------------------------------------------------
+  const admin2User = await prisma.user.upsert({
+    where: {
+      email_tenantId: {
+        email: "admin2@demo.com",
+        tenantId: demoTenant2.id,
+      },
+    },
+    update: {},
+    create: {
+      email: "admin2@demo.com",
+      passwordHash: adminPasswordHash,
+      firstName: "Demo",
+      lastName: "Admin2",
+      tenantId: demoTenant2.id,
+      roles: ["ADMIN"],
+      isActive: true,
+      isSuperAdmin: false,
+    },
+  });
+
+  console.log(`Admin2 user upserted: ${admin2User.email} (${admin2User.id})`);
+
   console.log("\nSeed complete. Test credentials:");
   console.log("  Admin:       admin@demo.com / admin123");
+  console.log("  Admin2:      admin2@demo.com / admin123");
   console.log("  Super-admin: superadmin@netforge.com / super123");
 }
 
diff --git a/src/app/api/admin/tenants/[id]/route.ts b/src/app/api/admin/tenants/[id]/route.ts
new file mode 100644
index 0000000..e06c2be
--- /dev/null
+++ b/src/app/api/admin/tenants/[id]/route.ts
@@ -0,0 +1,63 @@
+import { NextRequest, NextResponse } from "next/server";
+import { withSuperAdmin } from "@/lib/middleware/super-admin";
+import { prisma } from "@/lib/prisma";
+
+/**
+ * GET /api/admin/tenants/[id]
+ *
+ * Super-admin only: Returns single tenant details including user list.
+ * Returns 404 if tenant not found.
+ *
+ * Response shape:
+ *   { id, name, slug, status, ownerEmail, createdAt, users: [...] }
+ */
+export const GET = withSuperAdmin<{ id: string }>(
+  async (_req: NextRequest, _ctx, params) => {
+    const tenantId = params?.id;
+
+    if (!tenantId) {
+      return NextResponse.json({ error: "Tenant ID required" }, { status: 400 });
+    }
+
+    const tenant = await prisma.tenant.findUnique({
+      where: { id: tenantId },
+      include: {
+        users: {
+          select: {
+            id: true,
+            email: true,
+            firstName: true,
+            lastName: true,
+            roles: true,
+            isActive: true,
+            createdAt: true,
+          },
+        },
+        _count: {
+          select: { users: true },
+        },
+      },
+    });
+
+    if (!tenant) {
+      return NextResponse.json({ error: "Tenant not found" }, { status: 404 });
+    }
+
+    return NextResponse.json({
+      id: tenant.id,
+      name: tenant.name,
+      slug: tenant.slug,
+      status: tenant.status,
+      ownerEmail: tenant.ownerEmail,
+      businessAddress: tenant.businessAddress,
+      contactPhone: tenant.contactPhone,
+      createdAt: tenant.createdAt,
+      updatedAt: tenant.updatedAt,
+      suspendedAt: tenant.suspendedAt,
+      gracePeriodEndsAt: tenant.gracePeriodEndsAt,
+      userCount: tenant._count.users,
+      subscriberCount: 0,
+      users: tenant.users,
+    });
+  }
+);
diff --git a/src/app/api/admin/tenants/[id]/suspend/route.ts b/src/app/api/admin/tenants/[id]/suspend/route.ts
new file mode 100644
index 0000000..4c687e4
--- /dev/null
+++ b/src/app/api/admin/tenants/[id]/suspend/route.ts
@@ -0,0 +1,102 @@
+import { NextRequest, NextResponse } from "next/server";
+import { withSuperAdmin } from "@/lib/middleware/super-admin";
+import { prisma } from "@/lib/prisma";
+import { TenantStatus } from "@prisma/client";
+
+/**
+ * POST /api/admin/tenants/[id]/suspend
+ *
+ * Super-admin only: Suspend or activate a tenant.
+ *
+ * Request body: { action: "suspend" | "activate" }
+ *
+ * For "suspend":
+ *   - Sets status to PENDING_SUSPENSION
+ *   - Sets suspendedAt to now()
+ *   - Sets gracePeriodEndsAt to 7 days from now
+ *   - Returns message with grace period end date
+ *
+ * For "activate":
+ *   - Sets status to ACTIVE
+ *   - Clears suspendedAt and gracePeriodEndsAt
+ *   - Returns confirmation message
+ */
+export const POST = withSuperAdmin<{ id: string }>(
+  async (req: NextRequest, _ctx, params) => {
+    const tenantId = params?.id;
+
+    if (!tenantId) {
+      return NextResponse.json({ error: "Tenant ID required" }, { status: 400 });
+    }
+
+    // Parse request body
+    let body: { action?: string };
+    try {
+      body = await req.json();
+    } catch {
+      return NextResponse.json({ error: "Invalid request body" }, { status: 400 });
+    }
+
+    const { action } = body;
+
+    if (!action || (action !== "suspend" && action !== "activate")) {
+      return NextResponse.json(
+        { error: 'action must be "suspend" or "activate"' },
+        { status: 400 }
+      );
+    }
+
+    // Check tenant exists
+    const existing = await prisma.tenant.findUnique({
+      where: { id: tenantId },
+    });
+
+    if (!existing) {
+      return NextResponse.json({ error: "Tenant not found" }, { status: 404 });
+    }
+
+    if (action === "suspend") {
+      const now = new Date();
+      const gracePeriodEndsAt = new Date(now.getTime() + 7 * 24 * 60 * 60 * 1000);
+
+      const updated = await prisma.tenant.update({
+        where: { id: tenantId },
+        data: {
+          status: TenantStatus.PENDING_SUSPENSION,
+          suspendedAt: now,
+          gracePeriodEndsAt,
+        },
+      });
+
+      return NextResponse.json({
+        message: `Tenant suspension initiated. Grace period ends on ${updated.gracePeriodEndsAt?.toISOString()}.`,
+        tenant: {
+          id: updated.id,
+          status: updated.status,
+          suspendedAt: updated.suspendedAt,
+          gracePeriodEndsAt: updated.gracePeriodEndsAt,
+        },
+      });
+    } else {
+      // activate
+      const updated = await prisma.tenant.update({
+        where: { id: tenantId },
+        data: {
+          status: TenantStatus.ACTIVE,
+          suspendedAt: null,
+          gracePeriodEndsAt: null,
+        },
+      });
+
+      return NextResponse.json({
+        message: "Tenant activated.",
+        tenant: {
+          id: updated.id,
+          status: updated.status,
+          suspendedAt: updated.suspendedAt,
+          gracePeriodEndsAt: updated.gracePeriodEndsAt,
+        },
+      });
+    }
+  }
+);
diff --git a/src/app/api/admin/tenants/route.ts b/src/app/api/admin/tenants/route.ts
new file mode 100644
index 0000000..ef2f239
--- /dev/null
+++ b/src/app/api/admin/tenants/route.ts
@@ -0,0 +1,41 @@
+import { NextRequest, NextResponse } from "next/server";
+import { withSuperAdmin } from "@/lib/middleware/super-admin";
+import { prisma } from "@/lib/prisma";
+
+/**
+ * GET /api/admin/tenants
+ *
+ * Super-admin only: Lists ALL tenants on the platform (no tenant scoping).
+ * Returns tenant details including user count for monitoring purposes.
+ *
+ * Response shape:
+ *   Array of { id, name, slug, status, ownerEmail, createdAt, userCount, subscriberCount }
+ *   Sorted by createdAt descending (newest first).
+ */
+export const GET = withSuperAdmin(async (_req: NextRequest) => {
+  const tenants = await prisma.tenant.findMany({
+    orderBy: { createdAt: "desc" },
+    include: {
+      _count: {
+        select: { users: true },
+      },
+    },
+  });
+
+  const result = tenants.map((tenant) => ({
+    id: tenant.id,
+    name: tenant.name,
+    slug: tenant.slug,
+    status: tenant.status,
+    ownerEmail: tenant.ownerEmail,
+    createdAt: tenant.createdAt,
+    updatedAt: tenant.updatedAt,
+    suspendedAt: tenant.suspendedAt,
+    gracePeriodEndsAt: tenant.gracePeriodEndsAt,
+    userCount: tenant._count.users,
+    // subscriberCount: 0 until Subscriber model is added in Phase 2
+    subscriberCount: 0,
+  }));
+
+  return NextResponse.json(result);
+});
diff --git a/src/lib/middleware/super-admin.ts b/src/lib/middleware/super-admin.ts
new file mode 100644
index 0000000..b44d4b8
--- /dev/null
+++ b/src/lib/middleware/super-admin.ts
@@ -0,0 +1,93 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getCurrentUser } from "@/lib/auth";
+
+/**
+ * The context passed to super-admin route handlers.
+ * Handlers receive the session user confirmed to be a super-admin.
+ */
+export interface SuperAdminContext {
+  user: {
+    id: string;
+    email: string;
+    tenantId: string | null;
+    roles: string[];
+    isSuperAdmin: boolean;
+    firstName: string;
+    lastName: string;
+  };
+}
+
+/**
+ * Handler signature for super-admin route handlers.
+ * Receives the request and super-admin context with user info.
+ * Optionally receives route segment params (for dynamic routes).
+ */
+type SuperAdminHandler<P = Record<string, string>> = (
+  req: NextRequest,
+  ctx: SuperAdminContext,
+  params?: P
+) => Promise<NextResponse> | NextResponse;
+
+/**
+ * Higher-order function that wraps a Next.js route handler with super-admin enforcement.
+ *
+ * Flow:
+ *   1. Get current user session via getCurrentUser()
+ *   2. If no session → return 401 Unauthorized
+ *   3. If user.isSuperAdmin is not true → return 403 Forbidden
+ *   4. If authorized → call handler with super-admin context
+ *
+ * Usage (static route):
+ * ```typescript
+ * export const GET = withSuperAdmin(async (req, { user }) => {
+ *   const tenants = await prisma.tenant.findMany();
+ *   return NextResponse.json(tenants);
+ * });
+ * ```
+ *
+ * Usage (dynamic route with params):
+ * ```typescript
+ * export const GET = withSuperAdmin(async (req, { user }, params) => {
+ *   const { id } = params;
+ *   return NextResponse.json({ id });
+ * });
+ * ```
+ *
+ * @param handler - The route handler to wrap with super-admin protection
+ * @returns A Next.js route handler function
+ */
+export function withSuperAdmin<P = Record<string, string>>(
+  handler: SuperAdminHandler<P>
+) {
+  return async function (
+    req: NextRequest,
+    routeContext?: { params: P | Promise<P> }
+  ): Promise<NextResponse> {
+    // Step 1: Get session user
+    const user = await getCurrentUser();
+
+    // Step 2: No session → 401 Unauthorized
+    if (!user) {
+      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
+    }
+
+    // Step 3: Not super-admin → 403 Forbidden
+    if (!user.isSuperAdmin) {
+      return NextResponse.json(
+        { error: "Super-admin access required" },
+        { status: 403 }
+      );
+    }
+
+    // Step 4: Resolve params (Next.js 15 may return Promise<params>)
+    let resolvedParams: P | undefined;
+    if (routeContext?.params) {
+      resolvedParams = routeContext.params instanceof Promise
+        ? await routeContext.params
+        : routeContext.params;
+    }
+
+    // Step 5: Authorized → call handler with context and resolved params
+    return handler(req, { user }, resolvedParams);
+  };
+}