William Masters was an American gynecologist and sexologist, best known for his pioneering research on human sexuality. Along with his research partner, Virginia Johnson, he co-authored the influential book, "Human Sexual Response," published in 1966. Their work provided groundbreaking insights into the physiological aspects of sexual arousal and response. Masters and Johnson established the Masters and Johnson Institute, where they conducted clinical studies and therapy sessions to better understand sexual dysfunction. Their research significantly impacted the fields of psychology and medicine, helping to destigmatize discussions about sexual health and improve treatment options for individuals facing sexual issues.