Serious Sam II (or Serious Sam 2) is a science fiction first-person shooter video game released for the PC and Xbox and the sequel to the 2001 computer game Serious Sam.

In the single-player campaign, the player assumes the role of hero Sam “Serious” Stone in his adventures against the forces of the extraterrestrial overlord, “Mental”, who seeks to destroy humanity. Taking place after the events of Serious Sam: The Second Encounter, Sam travels through various different worlds collecting parts of a medallion in an effort to defeat Mental.