William D. Delahunt (born July 18, 1941) is a former U.S. Representative for Massachusetts's 10th congressional district, serving from 1997 to 2011. He is a member of the Democratic Party. Delahunt did not seek re-election in 2010, and left Congress in January 2011. He was replaced by Norfolk County District Attorney Bill Keating. He is currently an attorney with the firm of Eckert Seamans Cherin & Mellott.