主从式架构 (Client–server model) 或客户端-服务器（Client/Server）结构简称C/S结构，是一种网络架构，它把客户端 (Client) （通常是一个采用图形用户界面的进程）与服务器 (Server) 区分开来。每一个客户端软件的实例都可以向一个服务器或应用进程服务器发出请求。有很多不同类型的服务器，例如文档服务器、游戏服务器等。

主从式架构通过不同的途径应用于很多不同类型的应用进程，最常见就是目前在因特网上用的网页。例如，当你在维基百科阅读文章时，你的电脑和网页浏览器就被当做一个客户端，同时，组成维基百科的电脑、数据库和应用进程就被当做服务器。当你的网页浏览器向维基百科请求一个指定的文章时，维基百科服务器从维基百科的数据库中找出所有该文章需要的信息，结合成一个网页，再发送回你的浏览器。

The client–server model is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. Often clients and servers communicate over a computer network on separate hardware, but both client and server may reside in the same system. A server host runs one or more server programs which share their resources with clients. A client does not share any of its resources, but requests a server's content or service function. Clients therefore initiate communication sessions with servers which await incoming requests. Examples of computer applications that use the client–server model are Email, network printing, and the World Wide Web.