Gymea Bay are located in southern Sydney, in the state of New South Wales, Australia. Gymea Bay is 27 kilometres (17 min) south of the Sydney central business district, in the local government area of the Sutherland Shire. The postcode is 2227, which it shares with the adjacent suburb of Gymea.


The Gymea Bay locality takes its name from the adjoining Gymea Bay, a small bay on the north side of the Port Hacking estuary).

The locality includes only the single peninsula between Gymea Bay and the North West Arm of the Port Hacking River, bounded by Coonong Creek on the north and, on the west, by an unnamed creek flowing south of Gymea Bay Road between Barraran Street and Coonong Road. Gymea Bay became a locality within the suburb of Gymea. Early street directories show the locality of Gymea Bay as part of the suburb of Gymea.
The locality was characterised by large amounts of verdant bushland. However, since the 1980s, increased subdivision with smaller lots, larger houses and increased motor vehicle ownership has decreased the number of large trees.