Dan O'Brien is an American actor best known for his starring role as Mark, a police officer who lives next door to Whitney (Whitney Cummings) and Alex (Chris D'Elia), in the television sitcom Whitney, from 2011-2013.
O'Brien has worked extensively in theatre in New York City with The Atlantic Theater Company, MCC, The Present Company, The Flea Theater and The Vineyard Theater, among others.
In the UK, O'Brien has performed at the Camden People's Theatre in London and the Edinburgh Fringe Festival, garnering a Scotsman Fringe First Award for his work.
With his wife and playwright-in-residence, Julie Shavers, he has directed and produced four plays, including Silver Bullet Trailer, which was developed with the Royal Court Theatre and Present Company and performed at The Ohio Theater in New York.
O'Brien's film credits include Rebecca Gilman's Spinning into Butter and the David Letterman-produced The Greatest Movie Ever Made. Television appearances include How I Met Your Mother, Romantically Challenged and Delocated.
O'Brien is a graduate of the University of Notre Dame. He currently resides in Los Angeles with his wife and children.