Roger William Allam (born 26 October 1953) is an English actor, known primarily for his stage career, although he has performed in film, television and radio.

He played Inspector Javert in the original London production of the stage musical Les Misérables, First Officer Douglas Richardson in the award-winning radio series Cabin Pressure, and DI Fred Thursday in the TV series Endeavour. He is also known for his roles as Illyrio Mopatis in the HBO series Game of Thrones, Royalton in Speed Racer, Lewis Prothero in the 2005 adaptation of V for Vendetta and as Peter Mannion MP in The Thick Of It.

He has been nominated four times for the Laurence Olivier Award for Best Actor, winning twice.