Bonnet Bay is a suburb in southern Sydney, in the state of New South Wales, Australia that is located 29 kilometres (18 mi) south of the Sydney central business district in the local government area of the Sutherland Shire. Its postcode is 2226, which it shares with neighbouring Jannali and Como. Bonnet Bay is located on the eastern bank of the Woronora River, which flows north into the Georges River.

According to the 2021 Census, there were 2,238 residents in Bonnet Bay, with a median age of 44. In Bonnet Bay, 77.5% of people were born in Australia. The other most common countries of birth were England 5.5%, New Zealand 1.5%, China (excludes SARs and Taiwan) 1.0%, Scotland 0.8% and South Africa 0.8%. 88.3% of people only spoke English at home. Other languages spoken at home included Mandarin 1.5%, Cantonese 1.0%, Greek 1.0%, Spanish 0.8% and Russian 0.7%. The most common responses for religion in Bonnet Bay were No religion, so described 34.7%, Catholic 28.8%, Anglican 16.7%, Eastern Orthodox 3.4% and Uniting Church 2.9%.