Irvine Welsh's Ecstasy is a 2011 Canadian film adaptation of the short story "The Undefeated" from the best-selling book Ecstasy by Irvine Welsh. Directed by Rob Heydon, the film stars Adam Sinclair as Lloyd Buist, a drug user who smuggles ecstasy from Amsterdam. Kristin Kreuk plays his love interest, Heather Thompson.

Irvine Welsh is a Scottish novelist and short story writer. His 1993 novel Trainspotting was made into a film of the same name. He has also written plays and screenplays, and directed several short films.