Dean's Blue Hole is a blue hole located in Long Island, Bahamas in a bay located west of Clarence Town.
With a depth of , it is world's third deepest blue hole after the Taam Ja' Blue Hole in the Chetumal Bay and Dragon Hole in the South China Sea. The blue hole has a diameter of approximately 30 m but widens into a cavern with a diameter of 100 m.
It is believed that the blue hole was caused by either a fault in the limestone that allowed a corrosive solution to rise or that a buried cavern collapsed creating a sinkhole.
Due to its depth, Dean's Blue Hole is the site of a number of free diving world records.
In April 2010, New Zealander William Trubridge broke the world record reaching a depth of 92 m without the use of fins. Trubridge operated the Vertical Blue freediving competition at Dean's Blue Hole.
In July 2025, Walid Boudhiaf, set a new Tunisian national record of 118 m at Vertical Blue 2025. The 2025 competition featured 20-odd divers including Trubridge, Alenka Artnik, Alice Modolo, Arnaud Jerald, and Filippo Carletti.
One free diver, Nicholas Mevoli, however, died at Dean's Blue Hole in November 2013 attempting to set a new American national record.