Buckinghamshire is a large county in southern England, divided administratively into four regions. From north to south, these regions are Aylesbury Vale, High Wycombe, Chiltern and South Buckinghamshire. Formerly there was a fifth region in the form of Milton Keynes, but this broke off in 1997 to form its own unitary authority. Buckinghamshire is governed from its county town of Aylesbury, despite the largest and most important town in the county being High Wycombe. As the name suggests, Buckingham was formerly the county town; despite having lost this status, it remains the shire town.
Moving clockwise from the west, Buckinghamshire shares borders with Oxfordshire, Northamptonshire, Milton Keynes, Bedfordshire, Hertfordshire, Greater London and Berkshire. The largest towns in the county in order are High Wycombe, Aylesbury, Amersham, Beaconsfield, Buckingham and Princes Risborough. As mentioned previously, the county formerly included Milton Keynes, which is larger than any of these towns. It also formerly included Slough, which broke away in 1974 to join Berkshire. Slough is also larger than any of Buckinghamshire's current towns.