Netrek is an Internet game for up to 16 players, written almost entirely in cross-platform open-source software. It combines features of multi-directional shooters and team-based real-time strategy games. Players attempt to disable or destroy their opponents' ships in real-time combat, while taking over enemy planets by bombing them and dropping off armies they pick up on friendly planets. The goal of the game is to capture all the opposing team's planets.

Developed as a successor to 1986's Xtrek, Netrek was first played in 1988. It was the third Internet game, the first Internet team game, and as of 2022 is the oldest Internet game still actively played. It pioneered many technologies used in later games and has been cited as prior art in patent disputes. Xtrek and Netrek are the oldest games of what is now called the MOBA (multiplayer online battle arena) genre.