Wingletang Down is a Site of Special Scientific Interest (SSSI) on the southern side of the island of St Agnes in the Isles of Scilly, England, UK, which is noted for its biological characteristics.

[5] Wingletang Down is 71 acres (28.9 ha) of maritime heath, dune grassland and scrub reaching a maximum height of 66 feet (20 m) above sea level and is considered by Plantlife to be an Important Plant Area.

At the southern promontory of Horse Point there is short maritime grass and a tumble of large granite boulders where shallow temporary brackish pools occur.

[10][11][citation needed] The largest and easiest to find is adder's–tongue (Ophioglossum vulgatum) which is the commonest on the mainland but the rarest in Scilly and has not been seen in the Isles (on St Agnes) since 1990, or on Wingletang Down since 1938.

The probable reason for its late discovery is because the 0.79 inches (2 cm) fronds are found in the winter and turn yellow and disintegrate by early April which is before most botanists are in the area.

Since the withdrawal of grazing by cattle and, due to Myxomatosis, the fall in the population of rabbits (Oryctolagus cuniculus), some of the colonies are in danger of being smothered by competitive vegetation such as bracken (Pteridium aquilinum), European gorse and bramble.