Bletchley is a constituent town of Milton Keynes, Buckinghamshire, England. It is situated in the south-west of Milton Keynes, and is split between the civil parishes of Bletchley and Fenny Stratford and West Bletchley.

Bletchley is best known for Bletchley Park, the headquarters of Britain's World War II codebreaking organisation, and now a major tourist attraction. The National Museum of Computing is also located on the Park.

The town name is Anglo-Saxon and means Blæcca's clearing. It was first recorded in manorial rolls in the 12th century as Bicchelai, then later as Blechelegh (13th century) and Blecheley (14th-16th centuries). Just to the south of Fenny Stratford, there was Romano-British town, MAGIOVINIUM on either side of Watling Street, a Roman road.

Within the West Bletchley parish, in the Church Green district, is Bletchley Park, which, during the Second World War, was home to the Government Code and Cypher School. The German Enigma code was cracked here by, amongst others, Alan Turing. Another cipher machine was solved with the aid of early computing devices, known as Colossus. The park is now a museum, although many areas of the park grounds have been sold off for housing development.

Almost forty years after the construction of Bletchley railway station, the 1884/5 Ordnance Survey shows Bletchley as still just a small village around the C of E church at Bletchley Park, and a (separate) hamlet near the Methodist chapel and Shoulder of Mutton public house at the junction of Shenley Road/Newton Road with Buckingham Road. (These districts are known today as Old Bletchley and Far Bletchley). The major settlement of the time is nearby Fenny Stratford.