The historic county of Middlesex in south east England was represented in Parliament from the 13th century.
From early times the City of London and the rest of Middlesex had different sheriffs and other administrative arrangements.
The south west part of the historic county (then the Staines Urban District and the Sunbury on Thames Urban District but from 1974 the borough of Spelthorne) was transferred to the administrative county of Surrey.
In 1995 the village of Poyle, which had been a small area in the north of Spelthorne, was transferred to Berkshire.
The first part of this article covers the constituencies wholly or predominantly within the area of the historic county of Middlesex, both before and after the administrative changes of 1889 and 1965.