Ellen McLain is an American voice actress. She is best known for providing the voice of GLaDOS, the primary antagonist of the Portal video game series, the Combine Overwatch AI in Half-Life 2, and the Administrator, the announcer in Team Fortress 2. Her voice roles also include the Jaeger A.I. in Pacific Rim and The Witch in Left 4 Dead 2.

GLaDOS is a fictional character from the video game series Portal. The character was created by Erik Wolpaw and Kim Swift and voiced by Ellen McLain. GLaDOS is depicted in the series as an artificially superintelligent computer system responsible for testing and maintenance in the Aperture Science Computer-Aided Enrichment Center in all titles. While GLaDOS initially appears in the first game to simply be a voice that guides the player, her words and actions become increasingly malicious as she makes her intentions clear. The second game, as well as the Valve-created comic Lab Rat, reveals that she was mistreated by the scientists and used a neurotoxin to kill the scientists in the laboratory before the events of the first Portal. She is apparently destroyed at the end of the first game but returns in the sequel, in which she is supplanted by her former intelligence dampener and temporarily stuck on a potato battery, while her past as the human Caroline is also explored.