It is immediately south of Herm and has an area of approximately 44 acres (18 ha).
It is said that in AD 709 a storm washed away the strip of land that connected the island with Herm.
The Viking name for the island was Keitholm.
The island's name contains the Norman -hou suffix, meaning small island or small hill.
On the top is a marker. It is said that in earlier times, pirates were hanged on it with chains, as on nearby Crevichon.
From September 1964 until December 1971 the island was occupied by the Faed family consisting of Mr Angus Faed, his wife Susan Faed and their four children, Colin, Erik, Colette and Amanda. Mrs. Susan Faed was the 22nd tenant of Jethou.
In 1972, Charles Hayward, founder of the Firth Cleveland Group of Companies, purchased the Crown Tenancy of the island and lived there with his wife Elsie Darnell George until Sir Charles's death in 1983.
It is flanked by two islets, Crevichon to the north and Fauconniere to the south. There is one house on the island and two cottages as well as a large garage where vehicles such as quad bikes and tractors are stored.
Unlike the largely autonomous islands of Sark and Alderney within the Bailiwick, Jethou is administered entirely by the States of Guernsey, and elects members to the States of Deliberation as part of the St. Peter Port South electoral district.
At the back (east) of Jethou, puffins can be seen swimming off the rocks.