Harold Delf Gillies was a pioneering New Zealand plastic surgeon known as the "father of modern plastic surgery." During World War I, he established a plastic surgery unit in London and developed innovative techniques like pedicle flaps to reconstruct soldiers' severely damaged faces. After the war, Gillies opened a private plastic surgery clinic and helped establish plastic surgery as a medical specialty. He published influential textbooks and trained surgeons worldwide. Gillies performed some of the earliest gender reassignment surgeries and helped establish plastic surgery as a field that focused on both function and aesthetics. He is still considered the founder of modern plastic surgery.