The Indispensable Reefs are a chain of three large coral atolls in the Coral Sea. They are located about 50 km (30 mi) south of Rennell Island, separated from it by Rennel Trough. The chain stretches over a length of 114 km (71 mi) and its average width is 18 km (11 mi).
The three atolls are steep-to and each encloses a large deep lagoon. They are separated by deep passages two to three km (1.2–1.9 mi) wide. The atolls of the Indispensable Reef are aligned in a NW-SE direction:
- North Reef is 18 km (11 mi) long, and up to 7 km (4.3 mi) wide. The rim of the atoll has two narrow openings in the north and northwest. The reef has a total area of 100 km2 (39 sq mi), including lagoon and reef flat. There are no islets.
- Middle Reef is 51 km (32 mi) long. Little Nottingham Islet is a small islet located near the center of the reef. Besides its main lagoon, Middle Reef has a separate smaller northern lagoon. The total area is about 300 km2 (120 sq mi).
- South Reef is 21 km (13 mi) long and up to 8 km (5.0 mi) wide. It encloses a lagoon 18 to 35 metres (59 to 115 ft) deep. The total area exceeds 100 km2 (39 sq mi).
The ship Neptune struck Indispensable Reef on August 3, 1868 and was lost. The crew was rescued by the SS Boomerang.
During the Battle of the Coral Sea on May 7, 1942, two Japanese carrier attack planes B5N2 (EI-306 and probably EI-302) flying reconnaissance mission from the carrier Shokaku ditched on Indispensable Reef due to lack of fuel.
In the 1980s the Solomon Islands Government apprehended a vessel from Taiwan that had been poaching the giant clam stocks of Indispensable Reef. Corals and endangered fish species are also being plundered for the aquarium trade.
- Corals: "Solomon Islands" (PDF). World Atlas of Coral Reefs. 19 May 2003. pp. 330–333. Retrieved 6 June 2014.[dead link]
- Sunken ships: 
- Ecological concern: 
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