Frank J. Weber (August 7, 1849 – February 4, 1943) was a seaman, carpenter and union organizer from Milwaukee who between 1907 and 1926 served five (non-continuous) terms as a Socialist member of the Wisconsin State Assembly.
Weber was born in the city of Milwaukee on August 7, 1849. In 1852 his family moved to Grafton in Ozaukee County, and he attended public school in Ulao. After completing apprenticeship, Weber became an able seaman and sailed on Great Lakes and Atlantic Ocean merchant ships (according to his 1906 official biography, "in which capacity he visited all the most important seaports of the world").
He joined the Lake Seamen's Union in 1868, and was active in the Knights of Labor after 1869. In 1887 he helped organize the Milwaukee Federated Trades Council, becoming its secretary in 1902: an office he would hold until his retirement in January 1934. In 1888 Weber organized ship cargo handlers into what became the International Longshoremen's Association, and in the same year organized a Carpenters' Union in Milwaukee. In 1893 Weber was chosen the first president of the Wisconsin State Federation of Labor. As of 1894 he refused the title of President, preferring to be General Organizer; he was to hold that office until 1917. Weber fought to align the State Federation of Labor with the goals and principles of the Social Democratic Party (as it was long known in Wisconsin).