The Mark of Cain is a British Academy of Film and Television Arts Award-winning British television film first broadcast in 2007 following three young men as they experience the extremity of war for the first time, and the permanent effects of what they have seen and done as they return from their tour of duty. Rather than heroic stories, all they bring home are tawdry trophy photos, as well as the secrets of what they really did, until the consequences of their actions surface to confront them.

Produced by Red Production Company, it was originally scheduled on Channel 4 at 9 pm on 5 April 2007, but was rescheduled to 12 April 2007, in light of the detention of British service personnel by Iran. The film's title comes from Royal Irish Regiment Colonel Tim Collins's eve-of-battle speech in Iraq in 2003.