Slough (/slaʊ/) is a town and unparished area in the unitary authority of the same name in Berkshire, England, bordering west London. It lies in the Thames Valley, 20 miles (32 km) west of central London and 19 miles (31 km) north-east of Reading, at the intersection of the M4, M40 and M25 motorways. It is part of the historic county of Buckinghamshire. In 2020, the built-up area subdivision had an estimated population of 164,793. In 2011, the district had a population of 140,713.