Twofold Bay is located on the far south coast of New South Wales about 400 kilometres south of Sydney and 40 kilometres north of the Victorian border. The bay is divided into two distinct bights, Calle Calle Bay and Nullica Bay, giving Twofold Bay its name.
The tributaries of Twofold Bay include Boydtown Creek, Lake Curalo, Nullica River, Shadrachs Creek and Towamba River, in addition to other smaller creeks and stormwater drainages.
Twofold Bay is known for its whaling history. Humpback whales often come into the bay in spring. Eden is the largest commercial fishing port in New South Wales and a principal export point for timber and timber products. Twofold Bay also contains a commercial mussel farm.