Ray Milton Blanchard (; born October 9, 1945) is an American-Canadian sexologist, best known for his research studies on transsexualism, pedophilia and sexual orientation.
He found that men with more older brothers are more likely to be gay than men with fewer older brothers, a phenomenon he attributes to the reaction of the mother's immune system to male fetuses.
Blanchard has also published research studies on phallometry and several paraphilias, including autoerotic asphyxia.