The UB postcode area, also known as the Southall postcode area,[2] is a group of eleven postcode districts in England, within six post towns.

These cover parts of western and north-western Greater London, plus a very small part of Buckinghamshire.

The letters in the postcodes are the phonemic abbreviation of Uxbridge.

The main sorting office is in Greenford (Green Park Way) and the area served includes much of the London Borough of Hillingdon and the western part of the London Borough of Ealing, while the western part of UB9 covers a small part of Buckinghamshire, the southern part of UB2 covers a very small part of the London Borough of Hounslow, and a very small part of UB5 lies within the London Borough of Harrow.

The approximate coverage of the postcode districts: