William Paul Mitchell, better known by the stage name of Large Professor, is an American rapper and music producer. Based in New York City, he is known as a founding member of the underground hip hop group Main Source and as a mentor and frequent collaborator of Nas. About.com ranked Large Professor at No. 13 on its Top 25 Hip-Hop Producers list.

Main Source was a Canadian and American East Coast hip hop group based in New York City/Toronto, composed of Toronto-born DJs and producers, K-Cut and Sir Scratch, Queens DJ J.O.D and Queens MC and producer Large Professor. Later, another Queens MC, Mikey D, replaced Large Professor.