The Chiltern Hills form a chalk escarpment in South East England. They are known locally as the Chilterns. A large portion of the hills was designated officially as an Area of Outstanding Natural Beauty in 1965.

The Chilterns cover an area of 322 sq mi and are 11 mi at their widest and stretch 46 mi in a southwest to northeast diagonal from Goring-on-Thames in Oxfordshire, through Buckinghamshire, via Dunstable Downs and Deacon Hill in Bedfordshire, to near Hitchin in Hertfordshire.

The boundary of the hills is clearly defined on the northwest side by the scarp slope. The dip slope, by its nature, merges with the landscape to the southeast. Similarly, the Thames provides a clear terminal to the southwest, whereas northeast of Luton the hills decline slowly in prominence.