Birth name and background

Denis Colin Leary is his legal birth name; "Denis Leary" is not an alias. LOC lists Leary, Denis, born 1957 in Worcester (LOC). His parents were Irish Catholic immigrants from Killarney, County Kerry; he holds U.S. and Irish citizenship.

He studied and later taught comedy writing at Emerson College in Boston and built a tough-guy stand-up persona in the Boston club scene before national MTV exposure in the early 1990s.

Stand-up, film, and Rescue Me

Leary broke through with the MTV-era song/sketch "Asshole" and the HBO special No Cure for Cancer (1993), followed by Lock 'n Load (1997). Film roles include The Ref (1994), Wag the Dog (1997), and The Thomas Crown Affair (1999).

He co-created and starred as firefighter Tommy Gavin in FX's Rescue Me (2004–2011). After a 1999 Worcester warehouse fire killed six firefighters including a cousin, he founded the Leary Firefighters Foundation to support fire departments.

No Cure for Cancer comedy special/CD Rescue Me complete series DVD The Ref Blu-ray/DVD

Why the "real name" question matters

Search interest in a celebrity's "real name" usually means one of three things: a shortened everyday form (Tom for Thomas, Dave for David), a middle name used as a stage handle (Drake-style), or a true legal/professional change after immigration or branding. This sprint page states which case applies, cites library or encyclopedia authorities where possible, and avoids gossip. Career sections stay high-level and sourced so Domain Bot can add internal/external links without rewriting the biography. Living subjects are limited to public facts; memorials avoid graphic detail.