William Oscar Armstrong (March 10, 1847 – May 22, 1932) was an American politician who was the first black candidate for statewide office in Massachusetts.

After graduating from Oberlin College he performed missionary work in Haiti.

[11] Armstrong had two sons (William Jr. and Theodore) and three daughters (Martha, May, and Freida).

William O. Armstrong Jr. was the principal of the Dunbar School in Fairmont, West Virginia.

Frieda Armstrong was the first African-American woman to graduate from Boston University.