The O2 arena, referred to as North Greenwich Arena in the context of the 2012 Summer Olympics and 2012 Summer Paralympics, is a multi-purpose indoor arena located in the centre of The O2, a large entertainment complex on the Greenwich Peninsula in London. It is named after its main sponsor, the telecommunications company O2.

The O2 Arena has the second-highest seating capacity of any indoor venue in the UK, behind the Manchester Arena, but took the crown of the world's busiest music arena from New York's Madison Square Garden in 2008. The closest underground station to the venue is the North Greenwich station on the Jubilee line.

Following the closure of the Millennium Experience at the end of 2000, the Millennium Dome was leased to Meridian Delta Ltd. in 2001, for redevelopment as an entertainment complex. This included plans for an indoor arena.

Construction of the arena started in 2003 and finished in 2007. After the interior of the dome had been largely cleared and before building work inside began, in December 2004, the dome was used as the main venue for the annual Crisis Open Christmas organised by the London-based homelessness charity Crisis.

Owing to the impossibility of using cranes inside the dome structure, the arena's roof was constructed on the ground within the dome and then lifted. The arena building's structure was then built around the roof. The arena building, which houses the arena and the arena concourse, is independent from all other buildings in the O2 and houses all the arena's facilities. The arena building itself takes up 40% of the total dome structure.

The seating arrangement throughout the whole arena can be modified, similar to the Manchester Arena. The ground surface can also be changed between ice rink, basketball court, exhibition space, conference venue, private hire venue and concert venue.

The arena was built to reduce echoing, a common problem among London music venues. U2's sound manager, Joe O'Herlihy, worked with acoustic engineers to introduce measures such as sound absorbing material on the arena roof and the bottoms of strategically placed seats to reduce echoing.

Despite The O2 Arena being open for only 200 days per year (the equivalent of seven months), the venue sold over 1.2 million tickets in 2007, making it the third most popular venue in the world for concerts and family shows narrowly behind the Manchester Arena (1.25 million) and Madison Square Garden in New York City (1.23 million). By 2008 it had become the world's busiest venue with sales of more than two million, taking the crown from MEN Arena.

In May of 2011 the O2 arena was the site of the members of Pink Floyd, Roger Waters and David Gilmour reuniting and playing music from the acclaimed album The Wall, the first since the band's breakup.

During the 2012 Summer Olympics and Paralympics, The O2 Arena was referred as the North Greenwich Arena due to Olympics regulations regarding corporate sponsorship of event sites.

On September 25, 2013 Christine McVie Joined Fleetwood Mac on stage, marking her first live performance since 1998. She later re-joined the band officially in January 2014.

In 2014 the O2 arena hit controversy when guests were prevented from bringing food on site because they represented a terror threat. However, staff reportedly said that the food was banned because the food outlets were not making enough money.