Map of Union Banks

Vietnamese structure on Collins Reef (Đá Cô Lin)

Union Banks (Pagkakaisa Banks and Reefs) is a large drowned atoll in the center of Dangerous Ground in the Spratly Islands in South China Sea, 230 kilometres (120 nautical miles)^[1] west of the Philippine coast, containing islands and reefs whose ownership remains disputed and controversial.^[2] The closest atoll is Tizard Bank, 25 kilometres (13 nautical miles) due north of Union Banks. There are only two natural islands on the rim of the reef, Sin Cowe Island and Sin Cowe East Island.

The atoll is 55 kilometres (34 miles) long from Johnson South Reef in the southwest to Whitson Reef in the northeast, and up to 15 kilometres (9.3 miles) wide. Its total area measures 461 square kilometres (178 square miles). The central lagoon is up to 53 metres (174 feet) deep.^[3]

Islands and reefs comprising Union Banks

Union Banks consists of the following islands and reefs, clockwise starting in the southwest corner:^[4][5]

Key: yellow = occupied by PRC; violet = occupied by Vietnam

Chigua Jiao (Johnson South Reef)

Đá Cô Lin
(Collins Reef,
Johnson North Reef)

Loveless Reef

Gent Reef

Sinh Tồn (Sin Cowe Island)

Edmund Reef

McKennan Reef

Dōngmén Jiāo (Hughes Reef)

Hallet Reef

Holiday Reef

Empire Reef

Whitson Reef

Ross Reef

Sinh Tồn Đông (Grierson Reef/ Sin Cowe East Island)

Bamford Reef

Tetley Reef

unknown Reef

Jones Reef

Higgens Reef

Đá Len Đao (Landsdowne Reef)