Sean Ambrose is the main antagonist of the 2000 film Mission: Impossible II.
He is portrayed by Dougray Scott, who also portrays Stuart St. John.
Ambrose was an IMF agent who attempts to get his hands on a new virus called Chimera, as well as its cure, Bellerophon. Ambrose is sold the virus for £37,000,000, and he intends to release the virus into the population and then sell the cure to the highest bidder. At the beginning, Ambrose using Ethan Hunt's face while the latter was on holiday, steals the Chimera virus samples from Dr. Nekhorvich who had infected himself with a sample. Ethan Hunt is assigned the mission of recovering the virus with the help of 3 fellow agents (one of these being a professional thief named Nyah), and he manages to destroy a number of samples of the Chimera virus within the bio-chemical center Biocyte Pharmaceuticals. Before Ethan can destroy the final sample, Ambrose appears and engages in a firefight with Ethan. He forces Nyah to retrieve the virus for him, but she injects herself with it before he can stop her. Ambrose kidnaps Nyah and leaves, knowing that she is now valuable to him alive, but Ethan realizes that if he does not cure Nyah with Bellerophon within the next twenty hours, she will die along with a number of people in Sydney if left unchecked.
Ethan and his gang later track Ambrose and his men during a meeting and successfully steal the samples of Bellerophon from them. Ethan's men then locate Nyah on top of a cliff, who is about to commit suicide to prevent the Chimera virus inside her from spreading. Nyah is cured with the Bellerophon sample while Ethan and Ambrose have another firefight during a frantic motorcycle chase. The pair eventually fall onto a beach before engaging in hand-to-hand combat, with Ethan gaining the upper hand and apparently beating Ambrose to death. However, Ambrose, still alive, laughs triumphantly as he points a gun at Ethan's back. Ethan notices his own gun half buried in the sand by his feet and kicks it into the air, grabs it and spins round. As Ambrose fires, Ethan drops to the ground before shooting Ambrose three times in the chest and back, killing him.