Janek, played by Idris Elba, is a character in the film Prometheus.
Janek is captain of the Prometheus. Following Holloway's suggestion, he lands the ship near the structure containing the Juggernaut. During the expedition Janek remains on the Prometheus, observing the schematics which Fifield's spectagraphs develop.
He seduces Meredith Vickers while Fifield and Milburn radio for direction. Vickers and Janek recognize the Juggernaut as an Engineer ship. While Elizabeth Shaw prepares to join Peter Weyland on the expedition to awaken the Engineer, Janek says that the Engineers had nefarious intentions with the biological weapons and he will do whatever is necessary to protect Earth's interests.
When Vickers orders Janek to bring the Prometheus home, Shaw tells him that the Engineer ship is headed to Earth to release the black liquid and annihilate the human race. Janek decides to steer the Prometheus into the Engineer ship, and orders everyone to leave. Assistant pilots Chance and Ravel refuse and help Janek run the Prometheus into the Engineer ship, crippling it, sacrificing themselves, and saving the human race.