The O2 Arena is a multi-purpose indoor arena in the centre of The O2 entertainment complex on the Greenwich Peninsula in southeast London. It opened in its present form in 2007. It has the second-highest seating capacity of any indoor venue in the United Kingdom, behind the Manchester Arena, and in 2008 was the world's busiest music arena.

The arena was built under the former Millennium Dome, a large dome-shaped building built to house an exhibition celebrating the turn of the third millennium; as the structure still stands over the arena, The Dome remains a name in common usage for the venue.

In August of 2007, the rock star Prince, began the first of 21 sellout nights at the O2 Arena.

On 21 July 2007, British rock band Keane played the arena as part of their Under the Iron Sea Tour.

From 2008, the O2 Arena has hosted Capital's Jingle Bell Ball which is an annual mini-festival held over two nights, usually in early December.

During 2008, the Canadian singer Celine Dion performed two sold out shows, also in 2017 during her Celine Dion Live 2017 she performed four sold out shows and she will return on April 22 and 23, 2021 for her Courage World Tour.

Since 2009, the arena has hosted the ATP World Tour Finals, the season-ending finale of men's professional tennis, featuring the top eight players in the world. The venue has hosted the event for the second longest tenure, behind only Madison Square Garden (1977–89).

Cirque Du Soleil hosted Michael Jackson: The Immortal World Tour on 12, 13, 14, 16, 17 and 19 October through 21 of 2012.

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

Since March 2013, the arena has hosted C2C: Country to Country, Europe's largest country music festival, which annually attracts over 20,000 fans. UK and Irish acts, as well as up-and-coming American acts, perform sets several times across various pop-up stages in and around the arena, with the main stage accessible only to ticket-holders. The seventh C2C was held on 8–10 March 2019.

Since 2014, the Australia-based charismatic Christian church Hillsong has held the Hillsong Conference London at the arena.