Simonyi is a surname of Hungarian origin, and may refer to the following prominent figures who bear that name:
- András Simonyi, Hungarian ambassador to the United States
- André Simonyi, Hungarian-French former football player
- Charles Simonyi, software developer and space tourist
- Simonyi Professorship for the Public Understanding of Science, a chair at Oxford endowed by Charles Simonyi
- Károly Simonyi, Hungarian professor of electrical engineering and writer and father of Charles Simonyi
- Baron Lajos Simonyi, Hungarian politician
- Sándor Simonyi-Semadam, Hungarian politician and lawyer, Prime Minister of Hungary (1920)