Henry Havelock Ellis, known as Havelock Ellis (February 2, 1859 – July 8, 1939), was a British physician and psychologist, writer, and social reformer who studied human sexuality. He was co-author of the first medical textbook in English on homosexuality in 1897, and also published works on a variety of sexual practices and inclinations, including transgender psychology. He is credited with introducing the notions of narcissism and autoeroticism, later adopted by psychoanalysis. Like many progressive thinkers of his era, he supported eugenics and served as president of the Galton Institute. The 1897 English translation of Ellis' book Sexual Inversion, co-authored with John Addington Symonds and originally published in German in 1896, was the first English medical textbook on homosexuality.