William D. Delahunt (born July 18, 1941) has been a Democratic member of the United States House of Representatives since 1997, representing the 10th District of Massachusetts.
Born in Quincy, Massachusetts, Delahunt was educated at Thayer Academy, Middlebury College and Boston College Law School and later served in the United States Coast Guard Reserve. He served a term in the Massachusetts House of Representatives (1973–75) before serving as district attorney of Norfolk County for more than 20 years.
In February 2010, Delahunt announced that was considering retirement from Congress at the end of his present term. His retirement was confirmed on March 4th, 2010, by the Boston Globe.