Aguiar is a surname of Galician-Portuguese origin. Its etymology comes from the Latin word aquilare, translating to "eagle's nest".
Notable people with the surname include:
- Antone S. Aguiar Jr. (1930–2014), American judge and politician
- Bruno Aguiar, Portuguese footballer
- Ernani Aguiar, Brazilian composer, choral conductor, and musicologist
- Guma Aguiar, Brazilian-born American energy industrialist
- Henry Aguiar (born 1966), Venezuelan sprinter
- João Aguiar (writer) (1943–2010), Portuguese writer and journalist
- João Aguiar (swimmer) (born 1983), Angolan swimmer
- Joselia Aguiar, Brazilian writer
- Luis Aguiar, Uruguayan footballer
- Fernando Aguiar, Portuguese-born Canadian soccer player