J.T. Walsh (September 28, 1943–February 27, 1998) was an American actor best known for his roles as "quietly sinister white-collar sleazeballs" (quote from Leonard Maltin) in numerous feature films.

James Patrick Walsh was born in 1943. After returning from studying at Clongowes Wood College in Ireland he attended the University of Rhode Island, where he starred in many college theater productions. In 1974, he was discovered by a director and began working in off-broadway shows. He had intended to go by his real initials, but at a casting call, his name was misread as JT Walsh, and he realized he liked JT better than JP.

Walsh did not start doing feature films until 1983, where he had a minor role in Eddy Macon's Run. Over the next 15 years, he played in over 50 feature films, increasingly taking the bad guy role for which he is so well known. In his last year, he starred in Hidden Agenda, Pleasantville, and The Negotiator. All three of those movies were dedicated to his memory after he died from a heart attack on February 27, 1998. In addition, Jack Nicholson dedicated his Academy Award for As Good As It Gets to the memory of Walsh.

J.T. Walsh was the inspiration for Fametracker's The J.T. Walsh Memorial "Hey! It's That Guy!" feature on character actors.