The Industrial Union of Marine and Shipbuilding Workers of America (IUMSWA) was an American labor union which existed between 1933 and 1988.
The IUMSWA was first organised at the New York Shipbuilding Corporation shipyard in Camden, New Jersey. From here it slowly spread to a number of other private shipyards in the Northeast, gaining representation at the Staten Island shipyard in 1936 and the Federal Shipyard in 1937, as well as a range of other smaller ship repair yards in the New York area. The IUMSWA's industrial coverage of all production workers in the shipbuilding industry brought it into conflict with established craft unions, such as the boilermakers, leading the IUMSWA to be refused a AFL charter in 1933. The IUMSWA later joined the Congress of Industrial Organisations in 1936.
In 1940, the membership was about 100,000. IUMSWA gained size and strength during the World War II shipbuilding effort, and membership reached about 250,000. IUMSWA Local 15 signed a contract on May 15, 1941 covering workers at Bethlehem Steel Corporation's shipyard in Hoboken, New Jersey. This ended the company's policy of an open shop in shipbuilding, and was an important step towards the Steel Workers Organizing Committee (SWOC-CIO)'s success in the organizing the workers in Bethlehem's steel manufacturing plants.
The membership of the union declined after the war ended.
In the 1970s and 1980s, the union was known for its efforts in worker health and safety.
IUMSWA was merged with the International Association of Machinists in 1988.