Prosperous Bay Plain is an area on the north-eastern coast of Saint Helena

Saint Helena

Saint Helena , named after St Helena of Constantinople, is an island of volcanic origin in the South Atlantic Ocean. It is part of the British overseas territory of Saint Helena, Ascension and Tristan da Cunha which also includes Ascension Island and the islands of Tristan da Cunha...

, a British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 island territory in the South Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

. It is the site of the proposed Saint Helena Airport

Saint Helena airport

Saint Helena Airport is a proposed airport that will be constructed in the British Overseas Territory of Saint Helena, an island in the South Atlantic Ocean. From the 1960s there was an idea to build an airport on the St Helena Island. In 1999 this was taken up by the island government...

 and is notable for its high invertebrate

Invertebrate

An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

 biodiversity

Biodiversity

Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

.
Prosperous Bay Plain forms part of the eastern arid area of Saint Helena, and covers about 2.25 km², comprising one of the largest areas of relatively level ground on the island. It was formed 8.5 million years ago by lava flows from Saint Helena’s Southwest Volcano.