Carlyon Bay (Cornish: Porthmeur Wartha) is a bay and a set of three beaches (Crinnis, Shorthorn and Polgaver) near St Austell on the south coast of Cornwall, England, United Kingdom. It is located approximately 2 miles (3.2 km) east of the town centre.

Between 1920 and the Second World War, Carlyon Bay was the site of the New Cornish Riviera Lido and large sports facilities. After the war it became known as the Cornish Leisure World. A large venue, the Cornwall Coliseum, opened in the 1950s, it hosted exhibitions, tennis tournaments and concerts by musicians, but lost its importance with the opening of the Plymouth Pavilions in 1991. The venue continued until early 2003 when only the Gossips nightclub remained open, until its closure too shortly after. The building stood, falling into disrepair, until demolition began in April 2015.

Since the 1990s there have been plans for development of homes and a resort complex.

The area surrounding the bay was a centre of the mining industry and is now a golf course. The South West Coast Path runs along the cliff top and across the golf course. The Cliff Head Hotel was established in 1934 and stood until its demolition in 2017. Carlyon Bay is also the site of the Carlyon Bay Hotel, which stands upon and overlooks the cliff top with views of the bay.

In 1979 a scene for the film Dracula was filmed at Carlyon Bay and in 1986 the music video for Is This Love? by Alison Moyet was filmed on the beach.

Polgaver Beach is used by naturists.

The large rock on the foreshore is known as Stack Rock

The original 1990 planning permission for redevelopment into 500 homes was at first not realised, the main obstacle being the need for better sea defences.