Aldinga Beach is an outer southern suburb of Adelaide, South Australia. It lies within the City of Onkaparinga and has the postcode 5173. At the 2011 census, Aldinga Beach had a population of 9,697. The beach is a well-known spot for surfing, swimming, scuba diving, and snorkeling during the summer months. It overlooks an aquatic reserve which has been created to safeguard a unique reef formation.