Matthew "Mattie" Guinan (October 14, 1910 – March 22, 1995) was an American labor organizer who served as second president of Transport Workers Union of America (TWU).
Born in Offaly, Ireland, he immigrated in 1929. He took a job as a trolley operator in 1933. In 1943, after six years as an unpaid volunteer organizer, he became a full-time organizer for TWU Local 100.
He was able to negotiate a 40-hour work week for public and private bus workers. He became International Executive Vice President in 1952 and International Secretary Treasurer in 1956, and was re-elected in 1961 and 1965.
Following a bitter New York City transit strike (for which Guinan and other leaders spent nine days in jail after refusing to call it off), President Mike Quill died at age 60, and Guinan succeeded his longtime friend. Guinan held the post of International President until his retirement on May 1, 1979.
Guinan walked with Martin Luther King, Jr. in the 1965 march on Selma, Alabama and he committed the union's resources of money and manpower to the cause for equality.
As an AFL-CIO Vice President, he served on their Civil Rights Committee. His activism landed him on the master list of Nixon political opponents.
Cardinal John Joseph O'Connor presided over Guinan's 1995 funeral at St. Patrick's Cathedral, New York.