The London postal district includes all of the City of London, Camden, Hackney, Hammersmith and Fulham, Haringey, Islington, Kensington and Chelsea, Southwark, Tower Hamlets, Wandsworth and Westminster. Almost entirely included are Greenwich, Lambeth, Lewisham, Newham and Waltham Forest, except for a few streets. Barking and Dagenham, Barnet, Bexley, Brent, Bromley, Croydon, Ealing, Enfield, Harrow, Hounslow, Kingston upon Thames, Merton, Redbridge, and Richmond upon Thames are partly in the postal district. Havering, Hillingdon and Sutton are completely outside the postal district.

The London postal district is the area in England of 241 square miles (620 km2) to which mail addressed to the London post town is delivered. The General Post Office under the control of the Postmaster General directed Sir Rowland Hill to devise the area in 1856 and throughout its history it has been subject to reorganisation and division into increasingly smaller postal units, with the early loss of two compass points and a minor retraction in 1866. It was integrated by the Post Office into the national postcode system of the United Kingdom during the early 1970s and corresponds to the N, NW, SW, SE, W, WC, E and EC postcode areas. The postal district has also been known as the London postal area. The County of London was much smaller, at 117 square miles (300 km2), but Greater London is much larger at 607 square miles (1,570 km2).