Harold Delf Gillies performed one of the first sexual reassignment surgeries, termed gender affirmation surgeries as of 2022, on record in 1946 in London, England. He also practiced modern plastic surgery and helped distinguish it as a new branch of medicine in London, England, starting in the early 1900s. Gillies’s work focused initially on facial reconstructive surgery, particularly during both World War I and World War II. Gillies created newer and more efficient techniques that later became standard procedures for reconstructive and cosmetic surgeries. Gillies, along with two members in his practice, standardized over 11,000 techniques, and beginning in 1946, he performed one of the first successful phalloplasties on a transgender man, where he formed a new penis from the patient’s existing skin and tissue.