William Joseph Wynn (June 12, 1860 – January 4, 1935) was an American machinist and politician who served as a U.S. Representative from California for one term from 1903 to 1905.

He was an apprentice in the machinist's trade and subsequently worked in the principal manufacturing establishments of San Francisco.

He then served as member of the San Francisco Board of Supervisors from January 8, 1902, to March 4, 1903.

[2] He was an unsuccessful candidate for re-election in 1904 to the Fifty-ninth Congress, losing to Republican Everis A. Hayes.

[3] This article incorporates public domain material from the Biographical Directory of the United States Congress