Mark O'Brien (born May 7th, 1984) is a Canadian actor and director. He is best known for playing the role of Des Courtney in Republic of Doyle (2010) and Tom Rendon in Halt and Catch Fire (2014).
Known For

Nuremberg
Col. John Amen
2025

Shadow of God
Mason Harper
2025

Seven Veils
Paul
2025

Topper
Topper
2025

The Sticky
Charlie · (1 episode)
2024

61st Street
Officer Logan · (8 episodes)
2022

Blue Bayou
Ace
2021

The Righteous
Aaron Smith
2021

Your Honor
Father Jay · (3 episodes)
2020

Perry Mason
Thomas Milligan · (7 episodes)
2020

Hammer
Chris Davis
2019

Marriage Story
Carter Mitchum
2019

The Kelly Clarkson Show
(1 episode)
2019

Ready or Not
Alex Le Domas
2019

City on a Hill
Jimmy Ryan · (14 episodes)
2019

Goalie
Terry Sawchuk
2019

State Like Sleep
Darren
2019

The Front Runner
Billy Shore
2018

Bad Times at the El Royale
Larsen Rogers
2018

Kin
Jake
2018

The Darkest Minds
Rob Meadows
2018

How It Ends
Jeremiah
2018

Anon
Cyrus Frear
2018

Parallel
Josh
2018

The Last Tycoon
Max Miner · (9 episodes)
2017

Arrival
Captain Marks
2016

Wanderer
Eric
2016

The Dark Stranger
Mark
2016

How to Plan an Orgy in a Small Town
Bruce Buck
2015

Killjoys
Grayson Hicks · (1 episode)
2015

End of Days, Inc.
Jason
2015

Dennis
Dennis
2015

Halt and Catch Fire
Tom Rendon · (15 episodes)
2014

Hannibal
Randall Tier · (2 episodes)
2013
Sweetieface
Sam
2013

Beat Down
Michael
2012

Snarbuckled
Jacob O'Higgins
2010
Brad
Brad
2010

Republic of Doyle
Des Courtney · (77 episodes)
2010
Mum's the Word
Curtis
2009

Grown Up Movie Star
Will
2009

Warehouse 13
Jerry Hoffler · (1 episode)
2009
Cut from the Same Cloth
Jack Cochrane
2009

Heartless Disappearance Into Labrador Seas
Charlie
2008

The Four Horsemen
Eric Rollins
2008
The Voices of Our Mother
William
Epilogue
Henry
2008
The Embers and the Stars
Falsehood
Elizeus Carrier
Quiet at Dawn
Watts
2009

The One That Got Away
Tommy Palchek
2008
Better People
John
The Copenhagen Test
Cobb · (2 episodes)