Keith Matthew Thornton (born October 7, 1963), better known by his stage name Kool Keith, is an American rapper and record producer from The Bronx, New York City, known for his surreal, abstract and often profane or incomprehensible lyrics. Kool Keith has recorded prolifically both as a solo artist and in group collaborations. Kool Keith is generally considered to be one of hip-hop's most eccentric and unusual personalities.

Kool Keith was a cofounding member of Ultramagnetic MCs, whose debut Critical Beatdown was released in 1988. After two more albums with the group, Funk Your Head Up and The Four Horsemen, Kool Keith released his critically acclaimed solo debut album, Dr. Octagonecologyst under the name Dr. Octagon in 1996. He subsequently released a series of further independently released hip hop albums, including Sex Style, First Come, First Served (as Dr. Dooom), and most recently Keith.

After releasing only one album on a major label, Black Elvis/Lost in Space, Kool Keith subsequently returned to independently releasing music, producing further efforts as a solo artist and in collaboration with groups such as Analog Brothers, Masters of Illusion, Thee Undatakerz and Project Polaroid. Kool Keith has also made guest appearances in collaboration with Peeping Tom and Yeah Yeah Yeahs. He was also featured on the short track DDT on Jurassic 5's album Power in Numbers. The Prodigy's hit "Smack My Bitch Up" was based on a sample of Kool Keith's voice saying "Change my pitch up. Smack my bitch up" on Give The Drummer Some by Ultramagnetic MC's.