The opening ceremony of the 2012 Summer Olympics took place on the evening of Friday 27 July 2012 in the Olympic Stadium, London, during which the Games were formally opened by Queen Elizabeth II. As mandated by the Olympic Charter, the proceedings combined the ceremonial opening of this international sporting event (including welcoming speeches, hoisting of the flags and the parade of athletes) with an artistic spectacle to showcase the host nation's culture. The spectacle was entitled Isles of Wonder and directed by the Academy Award-winning British film director Danny Boyle, with Paulette Randall as associate director.

Prior to London 2012, there had been considerable apprehension about Britain's ability to stage an opening ceremony that could reach the standard set at the Beijing Summer Games of 2008. The 2008 ceremony had been noted for its scale, extravagance and expense, hailed as the "greatest ever", and had cost £65m. In contrast, London spent an estimated £27m (out of £80m budgeted for its four ceremonies), which was nevertheless about twice the original budget. Nonetheless, the London opening ceremony was immediately seen as a tremendous success, widely praised as a "masterpiece" and "a love letter to Britain".

The ceremony began at 21:00 BST and lasted almost four hours. It was watched by an estimated worldwide television audience of 900 million, falling short of the IOC's 1.5 billion viewership estimate for the 2008 ceremony, but becoming the most viewed in the UK and US. The content had largely been kept secret before the performance, despite involving thousands of volunteers and two public rehearsals. The principal sections of the artistic display represented Britain's Industrial Revolution, National Health Service, literary heritage, popular music and culture, and were noted for their vibrant storytelling and use of music. Two shorter sections drew particular comment, involving a filmed cameo appearance of the Queen with James Bond as her escort, and a live performance by the London Symphony Orchestra joined by comedian Rowan Atkinson. These were widely ascribed to Britain's sense of humour. The ceremony featured children and young people in most of its segments, reflecting the "inspire a generation" aspiration of London's original bid for the Games.

The BBC released footage of the entire opening ceremony on 29 October 2012, edited by Danny Boyle and with background extras, along with more than seven hours of sporting highlights and the complete closing ceremony.

The London Organising Committee of the Olympic and Paralympic Games (LOCOG) approached Danny Boyle to be the director of the ceremony in June 2010, and he immediately accepted. Boyle explained that there had been four things that made him take the job: he was a big Olympics fan, he lived a mile from the Stadium and so felt invested in the area, his late father's birthday was on the ceremony's date, and he felt his "Oscar clout" would enable him to push through what he wanted to do. He said it "felt weirdly more like a ... civic or national responsibility" to take the job.

Boyle acknowledged that the extravagance of the 2008 opening ceremony was an impossible act to follow — "you can't get bigger than Beijing" — and that this realisation had in fact liberated his team creatively. He said "..obviously I'm not going to try and build on Beijing, because how could you? We can't, and you wouldn't want to, so we're going back to the beginning. We're going to try and give the impression that we're rethinking and restarting, because they've (opening ceremonies) escalated since Los Angeles in 1984. They've tried to top themselves each time and you can't do that after Beijing." Beijing's budget had been £65m, whereas London's final budget was £27m, which was twice the original provision. The London stadium had the same number of seats as Beijing's, but was half the size; this intimacy of scale meant that Boyle felt he could achieve something personal and connecting.

The different sections of the ceremony were designed to reflect aspects of British history and culture, with the title Isles of Wonder partly inspired by Shakespeare's play The Tempest (particularly Caliban's 'Be not afeard' speech), and partly by the G. K. Chesterton aphorism: "The world shall perish not for lack of wonders, but for lack of wonder."

In July 2010, Boyle started brainstorming ideas with designer Mark Tildesley, writer Frank Cottrell-Boyce and costume designer Suttirat Anne Larlarb. They considered "what was essentially British", with the non-British Larlarb able to offer a view of what the world thought Britain meant. Cottrell-Boyce had given Boyle a copy of Pandaemonium, (named after the capital of Hell in Paradise Lost) by Humphrey Jennings, which collated contemporary reports from the Industrial Revolution. It had become traditional during the opening ceremony to "produce" the Olympic rings in a spectacular manner. Cottrell-Boyce commented: "Danny had a very clear idea that in the first 15 minutes you had to have a great, startling image that could go around the world; it had to climax with something that made people go 'Oh my God!'" Boyle decided that "the journey from the pastoral to the industrial, ending with the forging of the Olympic rings" would be that image.