Denis Leary is an actor/comedian/writer/director, whose father immigrated to Worcester from Ireland. He is a graduate of Emerson College in Boston, where he also taught comedy writing classes for five years after graduating. Leary is a distant cousin through marriage of Conan O'Brien; contrary to popular belief, they are not actually related through a recent common ancestor.

Leary first became famous through an MTV sketch in which he ranted about REM. He has also released two records of his stand-up comedy: No Cure for Cancer (1993) and Lock n' Load (1997). No Cure for Cancer was written with contributions from the English comedians Frank Skinner and David Baddiel when Leary was forced to stay over in London for a short period due to his son's premature birth there and ensuing health problems.

In 1994, his sardonic commentary song on the American lower-middle-class male, "Asshole", achieved much notoriety. It was voted #1 in a major Australian youth radio poll, the Triple J Hottest 100, and the video became a late-night MTV staple. Due to its explicit and controversial content, however, it received limited airplay on mainstream American radio stations.

Although he says he is most at home on stage doing stand-up, Leary has appeared as an actor in over 40 movies, including The Match Maker, The Virgin Suicides, The Ref, Wag the Dog, and Demolition Man. He also provided voices for characters in animated films such as the sabertoothed tiger 'Diego' in Ice Age and 'Francis' in A Bug's Life. Leary also produces numerous movies, television shows, and specials, including Comedy Central's Shorties Watching Shorties and the movie Blow, through his production company, Apostle.