网络时间协定（英语：Network Time Protocol，NTP）是以封包交换把两台电脑的时钟同步化的通信协定。NTP使用UDP端口123作为传输层。它是用作抵销可变延迟的影响。

NTP是仍在使用中的最古老的通信协定之一（在1985年前开始）。NTP最初由德拉瓦大学的Dave Mills 设计，他与一群志愿者仍在维护NTP。

NTP与更简单的DAYTIME（RFC 867）和TIME（RFC 868）通信协定没有关连。

Network Time Protocol (NTP) is a networking protocol for clock synchronization between computer systems over packet-switched, variable-latency data networks. In operation since before 1985, NTP is one of the oldest Internet protocols in current use. NTP was originally designed by David L. Mills of the University of Delaware, who still oversees its development.