John Valby (born November 22, 1944)  is a musician and comedian who plays in barrooms and college campuses up and down the East Coast. Using an old-fashioned piano, he creates comedic, obscene parodies of classic songs. Known as "Dr. Dirty", he typically performs in a classic white tailcoat and black derby hat. His songs and shows focus mainly on sex and racial slurs, with a mix of current and historic people and events.
While Valby is best known for his "Dr. Dirty" act, he has recorded and produced pop and rock albums for himself and other artists. One unusual act he was responsible for producing was that of Buffalo Sabres defenseman Jim Schoenfeld, with whom Valby recorded two albums: 1972's Schony and its follow-up, The Key Is Love (1974). He also had a small role as a piano player in a Tijuana brothel in the 1983 film Losin' It, which featured an early performance by Tom Cruise.
As of August 2012, he lived in a house in Clarence; the house burned down due to suspected arson that month.