Joseph William Martin Jr. (November 3, 1884 – March 6, 1968) was an American Republican politician who served as the 44th speaker of the United States House of Representatives from 1947 to 1949 and 1953 to 1955. He represented a House district centered on his hometown of North Attleborough, Massachusetts, from 1925 to 1967 and was the leader of House Republicans from 1939 until 1959, when he was ousted from leadership after the party's disastrous losses in the 1958 elections. He was the only Republican to serve as Speaker in a sixty-four year period from 1931 to 1995. He was a "compassionate conservative" who opposed the New Deal and supported the conservative coalition of Republicans and southern Democrats.

Early in his career, Martin worked as a newspaper editor and served in both houses of the Massachusetts General Court. He won election to the United States House of Representatives in 1924. He was elected House Minority Leader after the 1938 elections. He also served as Chairman of the Republican National Committee from 1940 to 1942 at the behest of Wendell Willkie, the 1940 Republican presidential nominee. Martin presided over five Republican National Conventions and frequently became involved in presidential politics. He urged General Douglas MacArthur to seek the 1952 Republican presidential nomination, and supporters of Robert A. Taft accused Martin of favoring Dwight D. Eisenhower in Martin's role as chairman of the contentious 1952 Republican National Convention. After Eisenhower won the 1952 election, Martin supported Eisenhower's internationalist foreign policy.

Martin lost his position as Republican leader after the party lost seats in the 1958 elections. He was succeeded by his more conservative deputy, Charles A. Halleck. Martin continued to serve in Congress until his defeat in the 1966 Republican primary by Margaret Heckler. Martin died in Hollywood, Florida, in 1968.

Martin was a Zionist who supported the recognition of the state of Israel.

Joseph Martin was born in North Attleborough, Massachusetts, the son of Catherine (née Keating) and Joseph William Martin, a blacksmith. Keating was born in Ireland in 1862, immigrated from Dublin to New York City in 1878, and settled in Newark, New Jersey, where she met Martin Sr., and they married on July 2, 1882; because Martin was a Presbyterian, the union required a matrimonial dispensation, but because Martin Sr. was a Presbyterian, it was relatively easy to obtain. Martin Jr. graduated from North Attleborough High School, where he played shortstop on the school baseball team. He also played semi-professional ball in an intercity league, from which he earned ten dollars per game.

Martin served in the Massachusetts House of Representatives (1912–1914), Massachusetts Senate (1914–1917) and the United States House of Representatives (1925–1967). He was a presidential elector in 1920.

Martin was the Chairman of the Republican National Committee from 1940 to 1942, having been recruited to that position by presidential nominee Wendell Willkie, whose nomination came as a complete surprise to political pro Martin. During the New Deal, he stood out as a major opponent of Franklin D. Roosevelt's policies and opposed his internationalist outlook on foreign affairs. However, he supported a few New Deal measures, such as the establishment of the minimum wage.

During the 1940 presidential campaign, Martin achieved a measure of notoriety as one-third of President Roosevelt's famous denunciation of "Martin, Barton and Fish." The other two were fellow GOP House members Bruce Fairchild Barton and Hamilton Fish III.