Music, dance, theatre, cinema, art and architecture are on the agenda during the June 21-September 9 event, which spans the Olympic and Paralympic Games.
The 12-week arts festival is the climax of the four-year Cultural Olympiad, designed to showcase Britain's prominent place in the arts in the buildup to the Games.
Among the big names taking part will be British singer Damon Albarn, Australian actress Cate Blanchett, dissident Chinese artist Ai Weiwei and U.S. hip-hop star Jay-Z.
About 25,000 artists from all 204 participating Olympic nations will take part.
The London 2012 Festival will be the largest cultural celebration in our lifetime, said Ruth Mackenzie, director both of the Cultural Olympiad and London 2012 Festival.
With new work from the best musicians, comics, artists, film makers and more, there will be arts events taking place in unusual places all over the UK that will showcase the best in international culture when the eyes of the world are on us this summer, she told the official launch.
Organizers added that there would be 10 million free tickets available and a full brochure explaining what was happening and where would be distributed around the country and available on the website www.london2012.com/festival.
CONCERTS AND BOUNCY CASTLES
The arts extravaganza launches on Midsummer's Night, June 21, with a host of events including an open-air concert set against the backdrop of Stirling Castle in Scotland featuring conductor Gustavo Dudamel and the Simon Bolivar Symphony Orchestra of Venezuela.
Another highlight is expected to be Radio 1's Hackney Weekend starring Jay-Z, Rihanna, Florence + The Machine, will.i.am, Jessie J, Jack White, David Guetta and Tinie Tempah.
Stonehenge will be transformed in a free, fiery vision created by French outfit Compagnie Carabosse, while Jeremy Deller's full size bouncy castle version of the famous English landmark will tour the country.
Constanza Macras' dance theatre group will perform in the forests of North Wales with ancient Mabinogion myths interpreted through the prism of modern Cardiff nightlife, and Elizabeth Streb's daredevil troupe will be performing extreme action scenes on some of London's best-known buildings.
Also included in the festival is a major celebration of William Shakespeare, including the performance of all of his plays in different languages at London's Globe theatre.
A string quartet will take to the skies and perform in helicopters and cathedrals will play host to aerial acrobats.
People will not like everything but there will be something that everyone does like, Culture Secretary Jeremy Hunt said.
The Cultural Olympiad began in 2008, but attracted criticism for being unfocused while some of the projects were derided as pretentious and costly.
A poll in the Guardian newspaper showed that nearly three quarters of respondents did not fully understand the concept of the Cultural Olympiad.
Scandinavian artist Olafur Eliasson had an application for a one million pound project, exploring the benefits of taking a deep breath, turned down, while a tall column of mist due to be lit up above the River Mersey has faced delays due to aircraft safety concerns.
Royal Opera House chief executive Tony Hall and Mackenzie were brought in to turn the showcase around.