Middlesex is a county located in south east of England, however many parts of Middlesex are now commonly known as part of Greater London, with small sections in neighbouring counties.

Strictly speaking Middlesex as a concept is only kept in existence by many people continuing to name it as a county on postal addresses and other contributors such as Middlesex County Cricket Club, whose home ground is at Lord's in St John's Wood, just outside Central London. It is still loved despite it not having any form of administrative function etc.

People hearing about Middlesex assume it was/is a large county because of the amount of Greater London territory (West and North London and Westminster, with the Thames as its southern boundary) which lies within its borders. It is actually the second smallest county in the UK. Middlesex was established in the Anglo-Saxon system from the territory of the Middle Saxons. The largely low-lying county's soil is dominated by clay in its north and alluvium on gravel in its south.

Middlesex contains locations as diverse as Teddington (where the tidal Thames normally finishes), Enfield, Notting Hill, Ickenham, Ealing (where the famous film studios which produced so much early film comedy still exists), Hampstead and Southall.