| Disputed: | yes |
| Ladd Reef | |
| Type: | reef |
| Other Names: | Đá Lát (Vietnamese) 日積礁 / 日积礁 Rìjī Jiāo (Chinese) |
| Pushpin Map: | Spratly Islands relief |
| Location: | South China Sea |
| Coordinates: | 8.6658°N 111.6767°W |
| Archipelago: | Spratly Islands |
| Country Admin Divisions Title: | District |
| Country Admin Divisions: | Trường Sa District |
| Country Admin Divisions Title 2: | Township |
| Country Admin Divisions 2: | Trường Sa Township |
Ladd Reef (Vietnamese: Đá Lát; 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.[1]
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.[2] The Chinese name Rìjī Jiāo was coined in 1947 to replace the 1935 name Lādé Jiāo (拉德礁),[3] 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.[4]
This coral reef lies on a northeast-southwest axis, in length, in width, and spans over an area of 9.9km2. It is entirely submerged during high tide, but there are some stones jutting out of the sea during low tide.[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"). 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.[8]