The locality and suburb of Gymea Bay are located in southern Sydney, in the state of New South Wales, Australia.

Gymea Bay is 27 kilometres (17 mi) south of the Sydney central business district, in the local government area of the Sutherland Shire.

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.

These suggested boundaries remain contentious as the proposal to the NSW Geographical Names Board required community consultation.

Since the 1990s, invasions of feral deer from the Royal National Park have begun to negatively affect shrub and ground cover and regrowth of trees.

Development in the area has eradicated most of these lilies in the locality and suburb but they can still be found across the Port Hacking River in the Royal National Park.

There are Aboriginal rock markings and middens at the headlands of the North West Arm of Port Hacking.

With the opening of a railway line from Sydney to Sutherland in 1885, carts and coaches could reach Gymea Bay as the closest point on the Port Hacking River by relatively easy grades.

With the operation of the Sutherland to Cronulla tramway from 1911 to 1931 and the Sutherland to Cronulla railway with Gymea railway station opening in 1939, Gymea Bay developed from a rural area into a recreation and holiday area with fishing shacks and holiday homes.

Kemp's Cosy Cabins and Caravan Park operated on the south of the peninsula with cabins and camping sites from Ellesmere Road to the North West Arm of the Port Hacking River where it had a large two-storey sandstone boatshed and function hall.

Miss Cook's general store built new premises, demolished the old store and rebuilt then continued under new ownership, later the Post Office and butchers shop and St. Barnabus Church of England closed and, after some years, became a Council children's centre, the bus depot ceased operation and eventually the service station closed.

A prominent local real estate agent who resided in Alkaringa Road, Miranda, recognising the effect of "snob factor" on property values, began a campaign to have Alkaringa Road, Miranda re-identified as part of adjoining Yowie Bay or Gymea Bay.

One nonsense argument was that Alkaringa Road residents' children went to Gymea Bay Public School.

Sutherland Shire Council, also recognising the effect on property values and its consequent rate income, nominated huge changes to the established locality, making much of Gymea, north of Coonong Creek, and Alkaringa Road, Miranda as part of the suburb of Gymea Bay.