Species 125 was the Borg designation for a humanoid race which, by the 2360s, had been assimilated into the Collective.

One notable member of Species 125 was a Borg Queen, one of which was first encountered by Captain Jean-Luc Picard in 2366 before the Battle of Wolf 359. In 2375, the second Queen encountered stated the designation of her species when she kidnapped Seven of Nine. (Star Trek: First Contact; VOY: "Dark Frontier")