Oxford Street is a major road in the City of Westminster in the West End of London, running between Marble Arch and Tottenham Court Road via Oxford Circus. It marks the notional boundary between the areas of Fitzrovia and Marylebone to the north, with Soho and Mayfair to its immediate south. It is Europe's busiest shopping street, with around 300,000 daily visitors, and as of 2012^[update] had approximately 300 shops. It is designated as part of the A40, a major road between London and Fishguard, though it is not signed as such, and traffic is regularly restricted to buses and taxis.

The road was originally part of the Via Trinobantina, a Roman road between Essex and Hampshire via London. It was known as Tyburn Road through the Middle Ages when it was notorious for public hangings of prisoners at Tyburn Gallows. It became known as Oxford Road and then Oxford Street in the 18th century and began to change from residential to commercial and retail use, attracting street traders, confidence tricksters, and prostitution. Department stores began to dominate the streetscape in the early 20th century, the most imposing of all being Selfridges (which opened in 1909). The street suffered heavy bombing during World War II, and several longstanding stores including John Lewis & Partners were completely destroyed and rebuilt from scratch.

Despite competition from out-of-town shopping centres and online retailers, Oxford Street remains in high demand as a retail location, with many British retail chains having their flagship stores on the street, and having a number of listed buildings. Unlike nearby shopping streets such as Bond Street, it has retained an element of downmarket trading alongside more prestigious retail stores. Generally speaking, the eastern end of Oxford Street features a higher proportion of more downmarket retailers, fast food restaurants, and souvenir shops whilst more exclusive and upmarket stores can be found towards its western end which passes close to the wealthy Mayfair district. The construction of Crossrail (known subsequently as the Elizabeth line) in the 2010s and early 2020s has changed the eastern end of Oxford Street markedly, with several major buildings having to be demolished completely to facilitate its construction, which in turn has brought new retailers and entertainment venues to the area.

The annual switching on of Christmas lights by a celebrity has been a popular event since 1959. As a popular retail area and a main thoroughfare for London buses and taxis, Oxford Street has suffered from traffic congestion, pedestrian congestion, a poor safety record, and pollution. Various traffic management schemes have been implemented by Transport for London (TfL) and others, including a ban on private vehicles during daytime hours on weekdays and Saturdays (in place since the 1970s), widened pavements, and improved pedestrian crossings.

Oxford Street runs for approximately 1.2 mi (1.9 km) and is entirely within the City of Westminster. The road begins at St Giles Circus as a westward continuation of New Oxford Street, meeting Charing Cross Road, Tottenham Court Road (next to Tottenham Court Road station). It runs past Rathbone Place, Wardour Street, and Great Portland Street to Oxford Circus, where it meets Regent Street. From there it continues past New Bond Street, Bond Street station, and Vere Street, ending at Marble Arch. The route continues as Bayswater Road and Holland Park Avenue towards Shepherd's Bush.

The road is within the London congestion charging zone. It is part of the A40, most of which is a trunk road running from London to Fishguard (via Oxford, Cheltenham, Brecon, and Haverfordwest). Like many roads in Central London that are no longer through routes, it is not signposted with that number. Numerous bus routes run along Oxford Street, including the 55, 73, 94, 98, 159, 390, and Night Buses N8, N55, N73, N98 and N207.

Oxford Street follows the route of a Roman road, the Via Trinobantina, which linked Calleva Atrebatum (near Silchester, Hampshire) with Camulodunum (now Colchester) via London and became one of the major routes in and out of the city.

Between the 12th century and 1782, it was variously known as Tyburn Road (after the River Tyburn that crossed it north to south), Uxbridge Road (the name still used for the road between Shepherd's Bush and Uxbridge), Worcester Road, and Oxford Road. On Ralph Aggas' "Plan of London", published in the 16th century, the road is described partly as "The Waye to Uxbridge" followed by "Oxford Road", showing rural farmland at the present junction of Oxford Street and Rathbone Place. By 1678 it was known as the "King's Highway", and the "Road To Oxford" by 1682.