Great Britain at the 2008 Summer Olympics

Great Britain competed at the 2008 Summer Olympics in Beijing, China. The United Kingdom was represented by the British Olympic Association (BOA), one of only five National Olympic Committees to have competed in every modern Summer Olympic Games since the inaugural event in 1896. The team of athletes selected to compete for the UK was officially known as Team GB; the delegation of 549 consisted of 313 competitors (169 men and 144 women) accompanied by 236 officials. The team incorporated athletes from the whole of the UK, including Northern Ireland (whose citizens may be selected to represent either Great Britain or Ireland at the Olympics if they have elected to hold Irish citizenship). Additionally, three of the British Overseas Territories compete separately from Britain in Olympic competition, namely Bermuda, the British Virgin Islands and the Cayman Islands.

Great Britain's Olympic medal performance in 2008 was its best in a century; at the close of the Games, the overall medal count of 47 was the second highest ever achieved by Team GB. The total number of gold medals was the highest since the 1908 Summer Olympics, which Britain hosted in London. Following the retesting of samples in 2016 in connection with the Russian doping scandal, disqualifications led to four further bronze medals being awarded to Great Britain in athletics: both the men's and women's 4 × 400 metres relay teams were officially upgraded to bronze; Kelly Sotherton received her second reallocated bronze medal, in the women's heptathlon event (having also been part of the women's relay team); and Goldie Sayers was awarded the bronze medal for the women's javelin throw event. These four additional medals retrospectively increased Team GB's total medal count to 51.

Great Britain finished fourth overall in the Olympic medal table, a target that had previously been set by UK Sport (the public body responsible for distributing funding to elite sport) for the 2012 Summer Olympics, which was hosted by the UK in London; after Team GB's success in 2008, UK Sport considered whether to target third place for 2012. Team GB finished top of the medal tables in cycling, sailing and rowing, and third in swimming. The highest number of medals was won in cycling, with a total of 14, eight of which were gold. Britain also won gold medals in sailing, rowing, swimming, athletics, canoeing and boxing. There were several outstanding individual achievements: cyclist Chris Hoy was the first Briton in 100 years to win three gold medals at a single Olympic Games; Rebecca Adlington's double Olympic gold was the best performance by a British swimmer for a century; Ben Ainslie won a gold medal for the third successive Games to become the most decorated British Olympic sailor of all time; Rebecca Romero became the first British woman to win a medal in two different Olympic sports, winning a rowing silver in 2004 and a cycling gold in 2008; and Louis Smith was the first Briton to win an individual gymnastics medal since 1908.

As the UK was to host the 2012 Summer Olympics in London, the closing ceremony on 24 August included a London 2012 handover performance featuring football star David Beckham, singer Leona Lewis and musician Jimmy Page, as well as London mayor Boris Johnson and a London double-decker bus.