Chesil Beach, sometimes called Chesil Bank, is a tombolo in Dorset, southern England. It is a shingle beach is 29 kilometres - 18 miles long, 200 metres - 660 ft wide and 15 metres - 50 ft high.
The beach and the Fleet are part of the Jurassic Coast, a World Heritage Site, and the location for a book 'On Chesil Beach' by Ian McEwan. At the end of the beach next to the Isle of Portland, the beach curves round sharply to form Chesil Cove. This part of the beach protects the low lying village of Chiswell from flooding. The beach provides shelter from the prevailing winds and waves for the town of Weymouth and the village of Chiswell, which would otherwise probably not exist. From West Bay to Cliff End the beach is piled up against the cliff. At Cliff End a hollow forms behind the beach and at Abbotsbury a stretch of saline (or brackish) water called the Fleet lagoon begins. The Fleet is home to many wading birds and Abbotsbury Swannery, and fossils can be found in the sand and mud.
The origin of the beach has been argued over for some time. Originally it was believed that beach material was from the Budleigh Salterton pebble beds to the west and later from Portland to the south east. The differences between the pebbles on the beach and nearby sources is now put down to the Flandrian isostatic sea level rise, so the feature could also be considered a barrier beach or bar, that happens to connect the mainland to an island rather than a 'true' tombolo. Normally, tombolos are created due to the effects of the island on waves (through refraction) and to sediment transport, which usually produces a beach perpendicular to the mainland rather than parallel to it.
Because of the low population density of nearby areas and their proximity to the naval base on Portland, the beach and the Fleet were used for machine gun training and bouncing bomb testing for Operation Chastise in World War II.