You’ve probably seen his face. Maybe it was the sharp-jawed CIA agent in a Netflix binge, or perhaps a gritty Irish gangster in the Marvel universe. Honestly, Cillian O’Sullivan is one of those "overnight success" stories that actually took about fifteen years of hard grafting to happen. He’s got that specific kind of Irish-American charm that lets him slide from a period piece like Vikings into a sci-fi legacy role in Star Trek without breaking a sweat.
It's kinda wild how many people confuse him with other actors because he transforms so much for his roles. But make no mistake, the Cillian O’Sullivan movies and tv shows lineup is becoming one of the most diverse resumes in Hollywood.
The Breakthrough: From Cork to the CIA
Born in New York but raised in Cork, Ireland, O'Sullivan spent years working in Irish television. If you go back far enough, you'll find him in things like the Irish-language show Seacht or the BBC Northern Ireland drama 6Degrees. He was the classic "working actor"—consistent, talented, but waiting for that one role to kick the door down.
That door didn't just open; it got blown off the hinges with In From the Cold.
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In this 2022 Netflix hit, he played Chauncey Lew, a rogue CIA agent who blackmails a suburban mom (who happens to be a former Russian assassin) into working for him. It was a massive swing. Most people expected a standard spy thriller, but O'Sullivan brought a layer of moral ambiguity to Chauncey that made him more than just a guy in a suit with a gun. He was cold, calculated, yet strangely vulnerable.
Cillian O'Sullivan Movies and TV Shows: The Essential Watchlist
If you're trying to catch up on his work, you can't just stick to the big streaming hits. You have to look at the smaller, grittier projects where he really sharpened his teeth.
- Daredevil: Born Again (2025): This is the one everyone is talking about lately. Playing a character named Devlin, an Irish gangster with ties to the underworld, O’Sullivan fits perfectly into the dark, street-level vibe of the MCU's Hell's Kitchen. It’s a role that demands a certain physical presence, and he delivers.
- Star Trek: Strange New Worlds: Talk about a legacy. He stepped into the shoes of Dr. Roger Korby. For the uninitiated, Korby is a huge deal in Trek lore—he's the "Louis Pasteur of archaeological medicine" and, famously, the fiancé of Nurse Christine Chapel. O’Sullivan’s version has this subtle, dark edge that fans are already obsessing over.
- Maze (2017): If you want to see him in a high-stakes film, this is it. Based on the true story of the 1983 prison break from the HM Prison Maze, he played Bobby Storey. It's a tense, claustrophobic movie that shows off his ability to handle heavy political drama.
- Then You Run (2023): A Sky Original where he plays Orin. This show is a chaotic, dark-comedy thriller that basically feels like a fever dream. It’s a great example of him picking "weird" projects over safe ones.
Why He's Not Just "Another Irish Actor"
There’s a specific nuance Cillian brings to his characters. He doesn't just "play Irish." In fact, because he was born in the States, his accent work is flawless. He can do the New York procedural thing—he’s been in The Blacklist, Chicago P.D., and FBI: Most Wanted—just as easily as he can play a North Cork local.
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In Misty Button (2019), a dark comedy set in the Bronx, he played a lead role that won "Best Narrative Feature" at the San Luis Obispo International Film Festival. It’s a small indie film, but it’s arguably where he showed the most range before the big studios started calling.
He’s also not afraid of the "villain" tag. Whether it's a gangster in Daredevil or a morally gray agent in In From the Cold, he seems to gravitate toward guys who have a "smidge of darkness," as he once put it in an interview about his Star Trek role.
What’s Next for O’Sullivan?
As we move through 2026, the momentum isn't slowing down. His role as Dr. Roger Korby in Star Trek: Strange New Worlds Season 3 is the big one to watch, especially since that character has a very tragic, sci-fi heavy future ahead of him. There is also the film The Lost Princess, where he plays a tech billionaire named Alec Touati. It's a bit of a departure from his usual gritty roles, leaning more into adventure and romance.
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Basically, if you aren't following his career yet, you're going to be seeing him in your "Recommended for You" section every time you open a streaming app.
Next Steps for the Fan:
If you want to see the best of his work, start with In From the Cold on Netflix for the action, then switch over to Maze for the dramatic weight. If you're a Marvel fan, his episodes in Daredevil: Born Again are a must-watch to see how he handles the transition from Irish indie darling to big-budget antagonist. Keep an eye out for The Boy That Never Was, another 2024/2025 project that showcases his ability to handle complex, emotional storytelling.