Ladd Reef (Vietnamese: Đá Lát; Mandarin Chinese: 日積礁/日积礁; pinyin: Rìjī Jiāo) is a Vietnam-controlled reef in the Spratly group of islands, South China Sea.

China (PRC) and Taiwan (ROC) are also claimants of the reef.

[4] This coral reef lies on a northeast-southwest axis, 3 nautical miles (5.6 km; 3.5 mi) in length, 1 nautical mile (1.9 km; 1.2 mi) in width, and spans over an area of 9.9 square kilometres (990 ha; 2,400 acres; 3.8 sq mi).

[5] The reef is uninhabited but contains a Vietnamese lighthouse (built in 1994)[6] with the inscription Hải đăng đá Lát[7] (literally "Ladd Reef Lighthouse").

In 1945, towards the end of the Second World War, a Dutch submarine (HNLMS O-19) ran aground on Ladd Reef.