The Announcer

From TF2 Wiki

The Announcer is the mysterious disembodied voice that announces events during the match, berating the team upon failure and congratulating them on their success. The announcer appears to be a somewhat elderly woman with a piercing and authoritative demeanor which has been heard to break under extreme pressure. She announces events such as control points being captured, taking/dropping of the enemy/team intelligence, and whether the payload is nearing a checkpoint. Mysteriously, the announcer for both the RED and the BLU teams appear to be the same person. It has been speculated that she may either be a high-ranking official within the respective intelligence organisations, or even the CEO. Whatever her status, her authority is both respected and feared by those under her command.

She is voiced by Ellen McLain, who also played the voice of GLaDOS in Portal and the Overwatch in Half-Life 2.