Gaja is a surname. Notable people with the surname include:
Angelo Gaja (born 1940), owner of the Gaja Winery Elena Gaja (born 1946), Romanian mezzo-soprano opera singer Gabriela Gaja (born 1972), Mexican retired butterfly swimmer Giorgio Gaja, Italian jurist Leilani Gaja (born 1985), Japanese model and actress
Gaja (name), feminine given name