Middlesex
Ancient and 1889 extent of Middlesex
Geography
Status	Ceremonial county (until 1965) Administrative county (1889–1965)
1801/1881 area	181,320 acres (734 km2)
1911 area	148,701 acres (601.8 km2)
1961 area	148,691 acres (601.7 km2)
HQ	see text
Chapman code	MDX
History
Origin	Middle Saxons
Created	In antiquity
Succeeded by	1889: to County of London 1965: Greater London and small parts to Surrey and Hertfordshire
Demography
1801 population - 1801 density	818,129 4.5/acre
1881 population - 1881 density	2,920,485 16.1/acre
1911 population - 1911 density	1,126,465 7.6/acre
1961 population - 1961 density	2,234,543 15/acre
Politics
Governance	Middlesex County Council (1889–1965)
Banner of arms of Middlesex County Council
Subdivisions
Type	hundreds (ancient)

Middlesex is one of the historic counties of England and the second smallest by area. The county once contained the rich and politically independent City of London on its southern boundary. The county was affected by the expansion of London in the 18th and 19th centuries. From 1855 the south east was administered as part of London. When county councils were initially introduced in England in 1889 around 20% of the area of Middlesex, and a third of its population, was transferred to the County of London.