The O2 Arena, London

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. The arena, as well as the overall O2 complex, is named after its primary sponsor, the telecommunications company O2, a subsidiary of Spain's Telefónica.

Despite being open for only 200 days per year, 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).

As of 2018, the O2 Arena was still the busiest music arena in the world in terms of ticket sales.