NetBIOS，为网络基本输入输出系统（英语：Network Basic Input/Output System）的缩写，它提供了OSI模型中的会话层服务，让在不同电脑上运行的不同程序，可以在局域网路中，互相连接，以及分享数据。严格来说，NetBIOS不是一种网络协定，而是应用进程接口（API）。较古老的操作系统，使用IEEE 802.2与IPX/SPX协定，可以使用NetBIOS Frames协定或NetBIOS over IPX/SPX协定来运作。现代操作系统，多数都使用TCP/IP协定，则可透过NetBIOS over TCP/IP协定来相互通信。

NetBIOS /ˈnɛtbʌɪ.ɒs/ is an acronym for Network Basic Input/Output System. It provides services related to the session layer of the OSI model allowing applications on separate computers to communicate over a local area network. As strictly an API, NetBIOS is not a networking protocol. Older operating systems ran NetBIOS over IEEE 802.2 and IPX/SPX using the NetBIOS Frames (NBF) and NetBIOS over IPX/SPX (NBX) protocols, respectively. In modern networks, NetBIOS normally runs over TCP/IP via the NetBIOS over TCP/IP (NBT) protocol. This results in each computer in the network having both an IP address and a NetBIOS name corresponding to a (possibly different) host name.