William J. Spencer (1867–1933) was an American labor leader who was secretary-treasurer of the Building Trades Department of the American Federation of Labor from its founding nearly continuously until his death in 1933.
Spencer was elected secretary-treasurer of the international Plumbers' union in 1897.
In 1903, Spencer was elected secretary-treasurer of the Structural Building Trades Alliance (SBTA).
He served until 1908, when the SBTA affiliated with the American Federation of Labor (AFL) and became the Building Trades Department (BTD).
This biographical article about a workers' rights activist is a stub.