Large Professor (born William Paul Mitchell on March 21, 1973 in Harlem, New York City, New York. USA), also known as Large Pro and Extra P., is a New York City-based hip hop rapper and record producer. 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.