The Undercliff is the name of several areas of landslip on the south coast of England. They include ones on the Isle of Wight; on the Dorset-Devon border near Lyme Regis; on cliffs near Branscombe in East Devon; and at White Nothe, Dorset. All arose from slump of harder strata over softer clay, giving rise to irregular landscapes of peaks, gullies and slipped blocks, that have become densely vegetated due to their isolation and change of land use. The Kent coast at Folkestone and Sandgate also has similar undercliff areas.
The Undercliff on the Isle of Wight skirts the southern edge of the island from Niton to Bonchurch. A favourable climate here has resulted in a semi-tropical environment, covered by lush vegetation.
The microclimate of warm sunshine, moist air and few winter chills was recognised by leading physicians in Victorian times as a beneficial environment for sufferers of respiratory diseases. This led to the establishment by Arthur Hill Hassall of a chest hospital at Ventnor.
The development of Ventnor and St Lawrence during the mid-19th century saw the construction of many fine houses and villas, and the creation of some beautiful gardens. These developments included the now-demolished Steephill Castle, and a number of houses built for the industrialist William Spindler in the 1880s.
The Undercliff is mostly accessible by a road, Undercliff Drive, running its length from Niton to Ventnor. It can be accessed by foot along the Isle of Wight Coastal Path.