服务器消息区块（英语：Server Message Block，缩写为SMB，服务器消息区块），又称网络文档共享系统（英语：Common Internet File System，缩写为CIFS），一种应用层网络传输协议，由微软开发，主要功能用是使网络上的机器能够共享计算机文档、打印机、串行端口和通讯等资源。它也提供认证的行程间通信机能。它主要用在装有Microsoft Windows的机器上，在这样的机器上被称为Microsoft Windows Network。

经过Unix服务器厂商重新开发后，它可以用于连接Unix服务器和Windows客户机，执行打印和文档共享等任务。

In computer networking, Server Message Block (SMB), one version of which was also known as Common Internet File System (CIFS, /ˈsɪfs/), operates as an application-layer network protocol mainly used for providing shared access to files, printers, and serial ports and miscellaneous communications between nodes on a network. It also provides an authenticated inter-process communication mechanism. Most usage of SMB involves computers running Microsoft Windows, where it was known as "Microsoft Windows Network" before the subsequent introduction of Active Directory. Corresponding Windows services are LAN Manager Server (for the server component) and LAN Manager Workstation (for the client component).