Boros (ボロス, Borosu), also called Lord Boros (ボロス様, Borosu-sama) by his subordinates, was the leader of the Dark Matter Thieves, a group of alien invaders responsible for the destruction of A-City. Like Saitama, Boros faced a self-imposed existential crisis, having become so powerful that no battle thrilled him. His intergalactic travels in search of a worthy opponent led him to Earth, where he was killed by Saitama.

Boros is the main antagonist of the Alien Conquerors Arc.