Mark O'Brien (born May 7, 1984, in St. John's, Newfoundland) is a Canadian actor, writer and director. He is best known for playing Des Courtney in Republic of Doyle (2010-2014) and Tom Rendon in Halt and Catch Fire (2015-2016), and he won the Canadian Screen Award for Best Actor for playing hockey goaltender Terry Sawchuk in the biographical drama Goalie (2019). He also wrote and directed the horror film The Righteous (2021), which picked up several festival awards.
His horror film The Voices of Our Mother, which he directed himself, was purchased by the streaming platform Shudder for release in the USA, Great Britain, Australia, and New Zealand.
The sci-fi film The Outer Threat featuring him, alongside Constance Wu and William Fichtner, had its sales rights acquired by The Coven.
He completed filming the low-budget sci-fi film The Embers and the Stars alongside Constance Wu and William Fichtner.
He appeared in the war drama Nuremberg in the role of Colonel John Amen.
