Belarus competed at the 2012 Summer Olympics in London, United Kingdom, from 27 July to 12 August 2012. This was the nation's fifth appearance at the Summer Olympics in the post-Soviet era. The Belarus Olympic Committee sent a total of 166 athletes to the Games, 90 men and 76 women, to compete in 20 sports.
Belarus left London with a total of 10 medals (2 gold, 5 silver, and 3 bronze), their lowest in Summer Olympic history. Most of these medals were awarded to athletes in sprint canoeing. Sergei Martynov, who won gold for the first time, became the most successful Belarusian shooter in history, with a total of three Olympic medals. Three Belarusian athletes set the nation's historical record to win Olympic medals for the first time in their sporting events, including swimmer Aliaksandra Herasimenia, who took two silver in women's freestyle events. Tennis players and Grand Slam titleholders Max Mirnyi and Victoria Azarenka, who also won the bronze in women's singles, became Belarus's first ever Olympic champions in the mixed doubles event, after beating Great Britain's Andy Murray and Laura Robson. For the first time in its history, Belarus, however, did not win an Olympic medal in athletics and wrestling.
Originally, Belarus had won three gold medals in the nation's total medal count. On 13 August 2012, the International Olympic Committee stripped shot putter Nadzeya Astapchuk of her gold medal after testing positive for the anabolic steroid metenolone, and the gold medal was subsequently awarded to silver medalist Valerie Adams from New Zealand.
Belarus Olympic Committee selected a team of 166 athletes, 90 men and 76 women, to compete in 20 sports, surpassing the record by just a single athlete short in Atlanta. Men's football was the only team-based sport in which Belarus had its representation in these Olympic games. There was only a single competitor in archery, and in badminton. Athletics was the largest team by sport, with a total of 49 competitors.
The Belarusian team featured five Olympic champions from Beijing (hammer throwers Aksana Miankova, sprint canoeing brothers Andrei and Aliaksandr Bahdanovich, and sprint kayakers Raman Piatrushenka, and Vadzim Makhneu). Shooters Sergei Martynov and Kanstantsin Lukashyk, and single sculls rower Ekaterina Karsten, competed at their sixth Olympic games, although they first appeared as part of either the Soviet Union (Martynov in 1988) or the Unified Team (Karsten and Lukashyk in 1992). Table tennis player Vladimir Samsonov became the fourth Belarusian athlete to compete at fifth Olympics. Meanwhile, trap shooter Andrei Kavalenka, at age 57, was the oldest athlete of the team, while rhythmic gymnast Nataliya Leshchyk was the youngest at age 17.
Professional tennis player Max Mirnyi, who won nine Grand Slam titles (including two from the U.S. Open) in his career, and competed at his fourth Olympics, became Belarus' flag bearer at the opening ceremony. Karsten, who won a total of five Olympic medals, served as the nation's team captain.
| width=78% align=left valign=top | The following is the list of number of competitors participating in the Games. Note that reserves in fencing, field hockey, football, and handball are not counted as athletes:
Belarus sent a total of 49 track and field athletes to the London games, after having achieved the required qualifying standards in their respective events (up to a maximum of three athletes in each event at the "A" standard, and one at the "B" standard). Hammer thrower and two-time Olympic medalist Ivan Tsikhan, was initially selected to the team, but IAAF decided to withdraw him from the competition, as a re-test of his sample from Athens was positive. On August 13, International Olympic Committee decided the shot putter Nadzeya Astapchuk, the nation's only track and field medalist, to strip off her gold medal at the London games after she was tested positive for the anabolic steroid metenolone.
<small><nowiki>*</nowiki> Initially awarded gold in the shot put, Astapchuk was disqualified, and stripped of her medal, following positive drugs tests during the Games.</small>
Belarus has so far qualified boats for the following events
<small>Qualification Legend: FA = Qualify to final (medal); FB = Qualify to final B (non-medal)</small>
<nowiki>*</nowiki> Maryia Lohvinava was reserve for the women's team pursuit but did not compete.
Belarus has qualified in the following events.
Belarus has qualified 3 fencers.
Belarus men's football team qualified for the event after win a play-off of the 2011 UEFA European Under-21 Football Championship.
Belarus has qualified four athletes in modern pentathlon.
Belarus has qualified 2 boats.
<small>Qualification Legend: FA=Final A (medal); FB=Final B (non-medal); FC=Final C (non-medal); FD=Final D (non-medal); FE=Final E (non-medal); FF=Final F (non-medal); SA/B=Semifinals A/B; SC/D=Semifinals C/D; SE/F=Semifinals E/F; QF=Quarterfinals; R=Repechage</small>
Belarus has so far qualified 1 boat for each of the following events
<small>M = Medal race; EL = Eliminated â did not advance into the medal race</small>
Belarus has ensured seven quota places in the shooting events at the Games.
Belarus sent a total of 8 swimmers at the London games, after having achieved qualifying standards in their respective events (up to a maximum of 2 swimmers in each event at the Olympic Qualifying Time (OQT), and 1 at the Olympic Selection Time (OST)): Belarus left London with a remarkable milestone in swimming, winning two silver medals by Aliaksandra Herasimenia in the women's 50 m freestyle and 100 m freestyle events, respectively.
Belarus has qualified two athletes for singles table tennis events. Based on their world rankings as of 16 May 2011 Vladimir Samsonov has qualified for the men's event and Viktoria Pavlovich for the women's.
Belarus has qualified three athletes for tennis events. After losing to U.S. tennis star Serena Williams in the semi-finals, Victoria Azarenka managed to win the bronze medal in the women's singles against Russia's Maria Kirilenko. The following day, Azarenka and her partner Max Mirnyi defeated Great Britain's Andy Murray, men's singles champion, and his partner Laura Robson to win the gold medal during the final match in the first ever mixed doubles event. Azarenka and Mirnyi, not only claimed the title, but also set the nation's historical milestone to their sport.
Belarus has qualified 4 men and 4 women.
Belarus has qualified eleven quotas.