Romeo Mathieu, CM (1917 – April, 1989) was a Canadian trade unionist, progressive political activist, and leading solidarity builder for the Quebec labour movement. Mathieu is best associated with his leading role in expanding the efforts of the United Packinghouse Workers of America (UPWA) into Quebec during the 1940s and 50s, and assisting with the merger between the UPWA and the Amalgamated Meat Cutters and Butcher Workmen of North America in 1968.