diff --git a/src/modules/notifications.types.ts b/src/modules/notifications.types.ts
new file mode 100644
index 0000000..a7bdd7d
--- /dev/null
+++ b/src/modules/notifications.types.ts
@@ -0,0 +1,83 @@
+export type NotificationChannel = "email" | "sms" | "push" | "in_app";
+
+export type NotificationPriority = "low" | "normal" | "high" | "urgent";
+
+/**
+ * A notification recipient.
+ */
+export type NotificationRecipient = {
+  userId: string;
+  channels?: NotificationChannel[];
+};
+
+export type NotificationTemplate = {
+  id: string;
+  name: string;
+  subject?: string;
+  body: string;
+  channel: NotificationChannel;
+};
+
+export type SendNotificationParams = {
+  recipientId: string;
+  templateId?: string;
+  channel: NotificationChannel;
+  subject?: string;
+  body: string;
+  priority?: NotificationPriority;
+  metadata?: Record<string, string | number | boolean>;
+  scheduledAt?: string;
+};
+
+export type BulkNotificationParams = {
+  recipientIds: string[];
+  templateId: string;
+  channel: NotificationChannel;
+  variables?: Record<string, string>;
+  priority?: NotificationPriority;
+};
+
+export type NotificationResult = {
+  id: string;
+  status: "queued" | "sent" | "delivered" | "failed";
+  sentAt?: string;
+  error?: string;
+};
+
+export type NotificationPreferences = {
+  userId: string;
+  enabledChannels: NotificationChannel[];
+  quietHoursStart?: string;
+  quietHoursEnd?: string;
+  unsubscribedTopics: string[];
+};
+
+export type ListNotificationsParams = {
+  status?: "queued" | "sent" | "delivered" | "failed";
+  channel?: NotificationChannel;
+  limit?: number;
+  skip?: number;
+};
+
+export interface NotificationsModule {
+  send(params: SendNotificationParams): Promise<NotificationResult>;
+
+  sendBulk(params: BulkNotificationParams): Promise<NotificationResult[]>;
+
+  getPreferences(userId: string): Promise<NotificationPreferences>;
+
+  updatePreferences(
+    userId: string,
+    preferences: Partial<Omit<NotificationPreferences, "userId">>
+  ): Promise<NotificationPreferences>;
+
+  list(params?: ListNotificationsParams): Promise<NotificationResult[]>;
+
+  /**
+   * Cancels a scheduled notification before it is sent.
+   *
+   * @param notificationId - The ID of the notification to cancel.
+   * @returns Promise resolving to `true` if the notification was successfully cancelled.
+   */
+  cancel(notificationId: string): Promise<boolean>;
+}