Sydney Anne Bristow is a graduate student in English in Los Angeles. She moonlights as an operative for SD-6, which she thinks is a black ops division of the CIA. Her fiancé is murdered in the pilot episode, and she learns SD-6 is actually a branch of an international criminal organization known as the Alliance of Twelve. She then becomes a double agent for the real CIA.
Sydney is highly skilled in Krav Maga and is fluent in many languages such as Russian, German, Greek, Dutch, French, Italian, Spanish, Portuguese, Norwegian, Swedish, Romanian, Hungarian, Hebrew, Uzbek, Arabic, Persian, Urdu, Indonesian, Cantonese, Mandarin, Japanese, Korean, Hindi, Vietnamese, Polish, Serbian, Czech, Ukrainian, and Bulgarian. Her code names are Bluebird, Freelancer, Mountaineer, and Phoenix.
Michael Vaughn is her main love interest throughout the series and eventually marries him. They have 2 children together.