The Isle of Sheppey is a small (36 square miles, 94 km≤) island off the northern coast of Kent, England in the Thames Estuary, some 38 miles (62km) to the east of central London. Sheppey is derived from the ancient Saxon "Sceapige", meaning isle of sheep, and even today the extensive marshes which make up a considerable proportion of the island provide grazing for large flocks of them. The island, like much of North Kent, comprises London Clay and is a plentiful source of fossils.
The land mass referred to as Sheppey consists of three main islands: Sheppey, the Isle of Harty and the Isle of Elmley (it was once known as 'The Isles of Sheppey', before the channels separating them silted up), but the marshy nature of the land to the south of the island means that it is so crossed by channels and drains as to consist of a multitude of islands. The ground is mainly low-lying, but at Minster rises to about 165ft.
Some Sheppey inhabitants like to call themselves Swampies, a term that began as, and for some people remains, an insult; for others it has become a term of endearment or a phrase for reinforcing identity.
Sheppey is separated from the mainland by a channel called the Swale. In common with the Wantsum Channel separating the Isle of Thanet from the mainland to the east; and Yantlet Creek at the Isle of Grain these were used in ancient times to allow shipping to reach ports such as Chatham and London without encountering the bad weather from the North Sea.
The largest town on the island is Sheerness. Other towns include Minster, which has a pebble beach, and Leysdown-on-Sea, which has a coarse sandy one. The whole north coast is dotted with caravan parks and holiday homes; there is also a naturist beach. The Royal Society for the Protection of Birds has a site at Elmley Marshes.