Olney is a market town and civil parish in the unitary authority area of the City of Milton Keynes, Buckinghamshire, England. At the 2011 Censu…Olney is a market town and civil parish in the unitary authority area of the City of Milton Keynes, Buckinghamshire, England. At the 2011 Census, it had a population of 6,477. Lying on the left bank of the River Great Ouse, the town is located around 8 miles from Central Milton Keynes, and 10 miles from Bedford, Northampton and Wellingborough.