Large Professor (born William Paul Mitchell on March 21, 1973, in Harlem, New York, New York. USA), also known as Large Pro and Xtra P, is a New York City-based hip hop record producer and emcee. He is also best known as a founding member of the influential underground hip hop group Main Source, and as mentor and frequent collaborator of Nas. About.com ranked Large Professor #5 on its Top 50 Hip-Hop Producers list.