Mark O'Brien

Acting • 72 Credits

Biography

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).

🎬 Directed Titles (4)

Directorial Filmography
The Righteous

The Righteous

2021 ⭐ 3.1
The Voices of Our Mother

The Voices of Our Mother

2026 ⭐ 3.2
Wanderer

Wanderer

2016 ⭐ 2.5
Kathy

Kathy

2011

✍️ Written & Story Credits (2)

Screenplay, Novel & Story
The Righteous

The Righteous

2021 ⭐ 3.1
Writer
The Voices of Our Mother

The Voices of Our Mother

2026 ⭐ 3.2
Writer

🎭 Acting Roles (30)

Ranked by Prestige & Popularity
Arrival

Arrival

2016 ⭐ 3.8
as Captain Marks
Marriage Story

Marriage Story

2019 ⭐ 3.9
as Carter Mitchum
Ready or Not

Ready or Not

2019 ⭐ 3.5
as Alex
Bad Times at the El Royale

Bad Times at the El Royale

2018 ⭐ 3.4
as Larsen Rogers
Hannibal

Hannibal

2013 ⭐ 4.1
as Randall Tier
The Darkest Minds

The Darkest Minds

2018 ⭐ 3.5
as Rob Meadows
How It Ends

How It Ends

2018 ⭐ 2.6
as Jeremiah
Anon

Anon

2018 ⭐ 3.0
as Cyrus Frear
Your Honor

Your Honor

2020 ⭐ 4.0
as Father Jay
Nuremberg

Nuremberg

2025 ⭐ 3.8
as Colonel John Amen
Kin

Kin

2018 ⭐ 3.0
as Jake
Warehouse 13

Warehouse 13

2009 ⭐ 3.8
as Jerry Hoffler
Halt and Catch Fire

Halt and Catch Fire

2014 ⭐ 4.0
as Tom Rendon
Killjoys

Killjoys

2015 ⭐ 3.5
as Grayson Hicks
Perry Mason

Perry Mason

2020 ⭐ 3.6
as Thomas Milligan
The Front Runner

The Front Runner

2018 ⭐ 3.0
as Billy Shore
Blue Bayou

Blue Bayou

2021 ⭐ 3.7
as Ace
City on a Hill

City on a Hill

2019 ⭐ 3.6
as Jimmy Ryan
Parallel

Parallel

2018 ⭐ 3.0
as Josh
How to Plan an Orgy in a Small Town

How to Plan an Orgy in a Small Town

2015 ⭐ 2.5
as Bruce Buck
The Copenhagen Test

The Copenhagen Test

2025 ⭐ 3.3
as Edmund Cobb
The Sticky

The Sticky

2024 ⭐ 3.6
as Charlie
The Kelly Clarkson Show

The Kelly Clarkson Show

2019 ⭐ 3.1
as Self
The Last Tycoon

The Last Tycoon

2017 ⭐ 3.5
as Max Miner
Shadow of God

Shadow of God

2025 ⭐ 2.8
as Mason Harper
Seven Veils

Seven Veils

2025 ⭐ 2.8
as Paul
State Like Sleep

State Like Sleep

2019 ⭐ 2.3
as Darren
Republic of Doyle

Republic of Doyle

2010 ⭐ 3.5
as Des Courtney
The Dark Stranger

The Dark Stranger

2016 ⭐ 2.5
as Mark
The Four Horsemen

The Four Horsemen

2008 ⭐ 3.1
as Eric Rollins