William Hackney Warren (February 11, 1884 – January 28, 1960), nicknamed "Hack", was a Major League Baseball player.

Warren played for the Indianapolis Hoosiers/Newark Pepper of the Federal League in 1914 and 1915.

He batted and threw right-handed.

He was born in Missouri and died at his home in Whiteville, Tennessee.

This biographical article relating to an American baseball catcher born in the 1880s is a stub.