Castlethorpe is a village and civil parish with a population of about 1000 in the unitary authority area of the City of Milton Keynes, Buckinghamshire, England. It is about 3 miles north-east of Stony Stratford, 4 miles north-west of Newport Pagnell and 7 miles north of Central Milton Keynes. It is separated from the county of Northamptonshire by the River Tove.