Chell

Chell is the protagonist of both Portal and Portal 2. Little is known about her past beyond her being abandoned at birth and her stubborn will to live. She wields only the Handheld Portal Device throughout her entire quest for freedom.

History
Little is known about Chell's history, GLaDOS repeatedly mentions during Portal 2 that she is an orphan whom was abandoned at birth, however GLaDOS' word is not considered reliable as she also made derogatory comments about throughout the game intending only to damage Chell's self-esteem.

Trivia

 * One of the Bring your daughter to work day science-fair entries within Portal 2 is signed, "by Chell"; implying Chell was the daughter of an Aperture Science employee. However there is no confirmed connection between this and the playable-character Chell.
 * The Turret song at the end of Portal 2 mentions Chell by name, calling her "cara mia" "my dear" in Italian. This implies a deeper connection between Chell and GLaDOS than was previously let on.