Mark O'Brien

May 7, 1984 (age 42) St. Johns, Newfoundland, Canada

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).

His titles like Arrival, Ready or Not, and Marriage Story - his biggest roles first.
Last updated: August 17, 2026

Watched: 0/30

Weighted avg: 6.85 /10

1

1

Arrival

2016November 2016 by Denis Villeneuve

Supporting as Captain Marks

Supporting as Captain Marks

7.29 Excellent--
2

2

Ready or Not

2019August 2019 by Matt Bettinelli-Olpin

Starring as Alex

Starring as Alex

6.69 Good
3

3

Marriage Story

2019September 2019 by Noah Baumbach

Minor role as Carter Mitchum

Minor role as Carter Mitchum

7.39 Excellent--
4

4

Bad Times at the El Royale

2018October 2018 by Drew Goddard

Minor role as Larsen Rogers

Minor role as Larsen Rogers

6.36 Good-
5

5

The Darkest Minds

2018July 2018 by Jennifer Yuh Nelson

Supporting as Rob Meadows

Supporting as Rob Meadows

6.60 Good
6

6

Anon

2018May 2018 by Andrew Niccol

Supporting as Cyrus Frear

Supporting as Cyrus Frear

5.53 Okay
7

7

How It Ends

2018July 2018 by David M. Rosenthal

Supporting as Jeremiah

Supporting as Jeremiah

4.77 Mediocre+
8

8

Nuremberg

2025November 2025 by James Vanderbilt

Supporting as Colonel John Amen

Supporting as Colonel John Amen

7.19 Good++
9

9

Kin

2018August 2018 by Josh Baker

Supporting as Jake

Supporting as Jake

5.62 Okay
10

10

The Front Runner

2018November 2018 by Jason Reitman

Supporting as Billy Shore

Supporting as Billy Shore

5.47 Okay
11

11

Parallel

2018April 2018 by Isaac Ezban

Lead role as Josh

Lead role as Josh

5.61 Okay
12

12

Blue Bayou

2021September 2021 by Justin Chon

Starring as Ace

Starring as Ace

6.91 Good+
13

13

How to Plan an Orgy in a Small Town

2015September 2015 by Jeremy LaLonde

Supporting as Bruce Buck

Supporting as Bruce Buck

4.94 Mediocre++
14

14

Shadow of God

2025March 2025 by Michael Peterson

Lead role as Mason Harper

Lead role as Mason Harper

5.59 Okay
15

15

The Copenhagen Test

2025 by Thomas Brandon

Supporting as Edmund Cobb

Supporting as Edmund Cobb

5.70 Okay+
16

16

The Last Tycoon

2017 by Billy Ray

Supporting as Max Miner

Supporting as Max Miner

6.03 Okay++
17

17

Seven Veils

2025March 2025 by Atom Egoyan

Supporting as Paul

Supporting as Paul

5.61 Okay
18

18

End of Days, Inc.

2015April 2015 by Jennifer Liao

Lead role as Jason

Lead role as Jason

5.74 Okay+
19

19

The Righteous

2021August 2021 by Mark O'Brien

Lead role as Aaron Smith

Lead role as Aaron Smith

5.96 Okay++
20

20

Hammer

2019December 2019 by Christian Sparkes

Starring as Chris Davis

Starring as Chris Davis

5.60 Okay
21

21

Republic of Doyle

2010–2014 by Allan Hawco

Supporting as Des Courtney

Supporting as Des Courtney

6.02 Okay++
22

22

The Dark Stranger

2016July 2016 by Chris Trebilcock

Supporting as Mark

Supporting as Mark

5.32 Okay-
23

23

State Like Sleep

2019January 2019 by Meredith Danluck

Supporting as Darren

Supporting as Darren

5.20 Okay--
24

24

The Four Horsemen

2008March 2008 by Sidney J. Furie

Lead role as Eric Rollins

Lead role as Eric Rollins

5.81 Okay+
25

25

The Outer Threat

2026July 2026 by William Woods

Starring as Daniel Ashford

Starring as Daniel Ashford

Needs more reviews
26

26

Grown Up Movie Star

2010January 2010 by Adriana Maggs

Supporting as Will

Supporting as Will

5.66 Okay
27

27

Goalie

2019March 2019 by Adriana Maggs

Lead role as Terry Sawchuk

Lead role as Terry Sawchuk

Needs more reviews
28

28

The Voices of Our Mother

2026June 2026 by Mark O'Brien

Starring as William

Starring as William

Needs more reviews
29

29

Topper

2025March 2025 by Kevin McNamara

Lead role as Topper

Lead role as Topper

Needs more reviews
30

30

The One That Got Away

2008April 2008 by Stacey Stewart Curtis

Minor role as Tommy Palchek

Minor role as Tommy Palchek

Needs more reviews