Ladd Reef (; Mandarin ) 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. Like Spratly Island, Ladd Reef lies to the west of the Philippines-defined "Kalayaan Islands" claim area.
The English name Ladd Reef was coined by Richard Spratly in late March 1843, after Captain Ladd of the ship Austen, who seemed to be the first to have seen the reef. The Chinese name Rìjë JiÃÂo was coined in 1947 to replace the 1935 name LÃÂdé JiÃÂo (æÂÂå¾·ç¤Â), which was transliterated from the English name Ladd.
Ladd Reef lies west of Dangerous Ground in the western half of the Spratly Islands, to the south of Coronation Bank, southwest of West London Reef (West Reef) and west of Spratly Island.
This coral reef lies on a northeast-southwest axis, in length, in width, and spans over an area of . It is entirely submerged during high tide, but there are some stones jutting out of the sea during low tide.
Da Lat Island, formerly known as Da Lat Islet, is the only islet situated on a coral reef. Initially, a permanent house was constructed on the island to serve as a station for the Vietnamese Navy. In 2018, a multifunctional cultural house was built there and was completed in October of the same year.
The geographical coordinates of this island, as recorded on the sovereignty marker, are 8ð40â²10â³N 111ð40â²23â³E (or 8.66944ðN 111.67306ðE). This location places it within the strategic and ecologically significant region of the South China Sea.
In early November 2022, Vietnam began land reclamation and renovation to transform Da Lat Islet into Da Lat Island. As of March 2025, Da Lat Island has an estimated reclaimed land area of around 55 hectares, stretching approximately 2.4 kilometers in length, with the potential for an airport to be constructed there.
The reef is uninhabited but contains a Vietnamese lighthouse (built in 1994) with the inscription Hải ÃÂÃÂng ÃÂá Lát (literally "Ladd Reef Lighthouse"). The lower portion of the lighthouse consists of quarters for a handful of Vietnamese soldiers and the lighthouse keeper.
In 1945, towards the end of the Second World War, a Dutch submarine (HNLMS O-19) ran aground on Ladd Reef.