Rapid Bay is a locality that includes a small seaside town and bay on the west coast of the Fleurieu Peninsula, South Australia. It lies within the District Council of Yankalilla and its township is approximately 100 km south of the state capital, Adelaide. A pair of jetties are popular attractions for recreational fishing, scuba diving and snorkelling. The bay particularly known as a site for observing leafy seadragons in the wild. Its postcode is 5204.

Rapid Bay features in the creation myths of the Kaurna and Ramindjeri peoples most notably as the burial site of the nephew of the Kaurna creator ancestor known as Tjilbruke. There is uncertainty as to the Kaurna name for Rapid Bay, which has been cited as Patparno, Patpangga (meaning "south" or "south place"), and Yarta-kulangga, a popular campsite at Rapid Bay, whose name probably means "place of the separate country". However, there is no evidence that any of these names was a place name for Rapid Bay, though the bay is officially dual-named Patpangga.

Prior to the establishment of the South Australian colony, whalers based on Kangaroo Island were known to have called at Rapid Bay though it was not so named until 1836. South Australia Colonial Surveyor General Colonel William Light made his first landfall on mainland South Australia at Rapid Bay on 8 September 1836. The site was named after Light's ship, the 162 ton brig Rapid. To mark this historic landfall the Colonel's initials, "W.L.", were carved into a large boulder – a replica is visible in the township, while the original is stored in the South Australian Museum, in Adelaide. John Rapid Hoare (7 November 1836 – perhaps 7 July 1916), also named for the brig Rapid, was the first European child born on mainland South Australia. Claims that he was born at Rapid Bay have been refuted.

Rapid Bay was briefly considered by Light as a potential site for the new colony's capital, but with the discovery of the Adelaide Plains it faded into quiet obscurity. On his first visit, Light created a garden then left the bay in the hands of Kangaroo Island sealers and indigenous people from the Encounter Bay area.

The BHP constructed the town, an ore-loading jetty and a high voltage power line from Willunga during the period 1938 to 1942 as part of the works undertaken to establish a limestone quarry. During the construction of the jetty, a worker named John Gamlin went missing and was presumed to have fallen from a platform that lacked rails and drowned. The tide was running quickly and wind speeds were reaching 40 miles per hour on the day of his disappearance.

Quarrying commenced in 1942. The limestone was transported by sea and used as a flux at BHP's Whyalla Steelworks in South Australia, and Newcastle and Port Kembla in New South Wales.

In 1948, production averaged 30,000 tonnes per month with a fully mechanised process from electric shovel to crushers, then by conveyor to ship. At that time there were 41 men employed at the project, including office staff.

BHP's assets, including a crushing plant, jetty and loading wharf, were eventually sold to Adbri in 1981.