The Chew Valley is an area in North Somerset, England, named after the River Chew, which rises at Chewton Mendip, and joins the River Avon at Keynsham. Technically, the area of the valley is bounded by the water catchment area of the Chew and its tributaries; however, the name Chew Valley is often used less formally to cover other nearby areas, for example, Blagdon Lake and its environs, which by a stricter definition are part of the Yeo Valley. The valley is an area of rich arable and dairy farmland, interspersed with a number of villages.
The landscape consists of the valley of the River Chew and is generally low-lying and undulating. It is bounded by higher ground ranging from Dundry Down to the north, the Lulsgate Plateau to the west, the Mendip Hills to the south and the Hinton Blewett, Marksbury and Newton Saint Loe plateau areas to the east. The valley's boundary generally follows the top of scarp slopes except at the southwestern and southeastern boundaries where flat upper areas of the Chew Valley grade gently into the Yeo Valley and eastern Mendip Hills respectively. The River Chew was dammed in the 1950s to create Chew Valley Lake, which provides drinking water for the nearby city of Bristol and surrounding areas. The lake is a prominent landscape feature of the valley, a focus for recreation, and is internationally recognised for its nature conservation interest, because of the bird species, plants and insects.