Jonathan "Jack" Donahue Bristow, played by Victor Garber, is a fictional character of the ABC television series Alias.

For playing the character, Garber received critical acclaim and three consecutive nominations for the Primetime Emmy Award for Outstanding Supporting Actor in a Drama Series, among other accolades.

Jack Bristow, a longtime agent of the CIA and former double officer with SD-6, is often emotionally distant and can be among the show's coldest and most brutal characters.

According to background information provided in the official Alias magazine, Jack Bristow is originally from Canada (reflecting the fact that actor Victor Garber is Canadian).

Several years later when Sydney herself becomes a double agent for the real CIA, she discovers that her father has long been in the same position and they learn to work together to bring down SD-6.

When Irina Derevko makes her reappearance in Season 2, Jack must also deal with his unresolved feelings of love and bitterness towards her while continuing to perform his job at SD-6 and the CIA.

Sydney initially believed that this programming had taken away her choices in life, but in Season 3 discovers that it had, in fact, protected her autonomy and made her immune to brainwashing by the Covenant.

Jack Bristow contracts radiation poisoning during the events of the fourth-season episode "Nightingale" when he entered a radioactive area in order to save Sydney's life during a mission.

During the impersonation, Sydney learned that her father had planned to leave the CIA in order to be a better parent to her and would have done so if her mother had not been revealed as a KGB agent.

In the absence of Michael Vaughn, the child's father, Jack attends doctor's visits with Sydney and helps her to assemble a crib for his grandchild's nursery.

In the final episode, Jack, Vaughn (recently returned from hiding) and Sydney mount an assault on Rambaldi's tomb in Mongolia where Sloane is in the process of activating The Horizon.

Critically wounded, Jack is taken outside and insists that Sydney leave him and go to Hong Kong in order to stop the final player in Rambaldi's endgame - Irina - and his daughter reluctantly obeys.