The O2 is a large entertainment district on the Greenwich peninsula in South East London, England, including an indoor arena, a music club, a Cineworld cinema, an exhibition space, piazzas, bars, and restaurants. It was built largely within the former Millennium Dome, a large dome-shaped canopy built to house an exhibition celebrating the turn of the third millennium; consequently The Dome remains a name in common usage for the venue. It is sometimes referred to as The O2 Arena, but that name properly refers to a smaller indoor arena within The O2. Naming rights to the district were purchased by the mobile telephone provider O2 from its developers, Anschutz Entertainment Group (AEG), during the development of the district. AEG owns the long-term lease on the O2 Arena and surrounding leisure space.
From the closure of the original "Millennium Experience" exhibition occupying the site, several ways of reusing the Millennium Dome's shell were proposed and then rejected. The renaming of the Dome in 2005 gave publicity to its transition into an entertainment district. The Dome's shell remained in situ, but its interior and the area around North Greenwich Station, the QE2 pier and the main entrance area were completely redeveloped.
The area is served by the Jubilee line's North Greenwich tube station, which was opened just before the millennium exhibition, and by bus routes. Thames Clippers operate a river boat service for London River Services; the present tenants, AEG, purchased Thames Clippers in order to provide river links between central London and The O2. As well as a commuter service, Thames Clippers operates the O2 Express service. Local buses also serve the station and the nearby O2.
On 23 February 2017, O2 announced that they had agreed to a deal with AEG to maintain the naming rights of The O2 for a further 10 years until 2027.