Buckinghamshire (, abbreviated Bucks), is a ceremonial county in South East England and one of the home counties. It is bordered by Northamptonshire to the north, Bedfordshire to the north-east, Hertfordshire to the east, Greater London to the south-east, Berkshire to the south, and Oxfordshire to the west. The largest settlement is the city of Milton Keynes, and the county town is Aylesbury.
The county has an area of 1,874 km2 (724 sq mi) and had a population of 840,138 at the 2021 census. Besides Milton Keynes (264,349), which is in the north-east, the largest settlements are in the southern half of the county and include Aylesbury (94,238), High Wycombe (75,814), and Chesham (21,483). For local government purposes Buckinghamshire comprises two unitary authority areas, Buckinghamshire and Milton Keynes. The historic county had slightly different borders, and included the town of Slough.
The Chiltern Hills, an Area of Outstanding Natural Beauty, occupy the south of the county and contain its highest point, Haddington Hill (267 m (876 ft)). The Chilterns are the source of the River Ouzel, which flows across the lowland Vale of Aylesbury in the north of the county and through Milton Keynes before meeting the River Great Ouse at Newport Pagnell. The Thames forms part of the county's southern boundary.
Notable service amenities in the county are Pinewood Film Studios, Dorney rowing lake and part of Silverstone race track on the Northamptonshire border. Many national companies have head offices or major centres in Milton Keynes. Heavy industry and quarrying is limited, with agriculture predominating after service industries.