Alien Front Online is a 2001 video game released for the Sega Dreamcast exclusively in North America. Alien Front Online is an online version of the arcade game Alien Front, where it was bundled with the Dreamcast Microphone.

In the game, players use armored vehicles to fight battles staged in arenas. Players could choose which side they wished to fight for, the aliens or the humans, and could also choose one of three different vehicles; each having its own advantages and disadvantages. Although the game was fully playable for one person, it was primarily designed as an online game in which up to 8 players (up to 4 on each side) could play. Players move around the arena attempting to shoot each other, while also looking for power-ups for their vehicles. Typically, the game was played for a set number of minutes, after which the team with the most kills would be declared the winners. If a player was killed while playing the game, they simply respawn.

Alien Front Online was originally slated for release in Japan, but was cancelled. A related game, simply titled Alien Front, was announced by Sega for the N-Gage in 2004, but was eventually canceled.

The game was brought back online by fans through private servers in 2016