GLaDOS

GLaDOS, known in full as the Genetic Lifeform and Disk Operating System, is the computer system designed to control and oversee Aperture Laboratories, as well as the guide of the Aperture Science computer-aided Enrichment Center.

GLaDOS is the main antagonist throughout Portal, and through the first half of Portal 2's single-player campaign.

Trivia

 * GLaDOS is voiced by Ellen McLain, who also voices the Administrator in Team Fortress 2 and the Combine Overwatch in the Half-Life 2 series.