The United States of America (USA), represented by the United States Olympic Committee (USOC), competed at the 2012 Summer Olympics in London, from July 27 to August 12, 2012. U.S. athletes have competed at every Summer Olympic Games in the modern era, except the 1980 Summer Olympics in Moscow which they boycotted in protest of the Soviet invasion of Afghanistan. The USOC sent a total of 530 athletes to the Games, 262 men and 268 women, to compete in 25 sports. For the first time in its Olympic history, the United States was represented by more female than male athletes.
U.S. athletes left London with a total of 104 medals (46 gold, 28 silver and 30 bronze), finishing at the top of the gold and overall medal standings. The 46-gold medal record was the most the United States had ever won in any Olympics in which it was not the host nation. At least one medal was awarded to U.S. athletes in sixteen sports, thirteen of which contained at least one gold. U.S. athletes dominated the nations' medal standings in swimming, wherein they won a total of 31 medals, including 16 golds. Twenty-seven U.S. athletes won more than a single medal. The U.S. team-based athletes also proved particularly successful, as the women's soccer, water polo, and volleyball teams won gold and silver medals, respectively. Furthermore, the men's and women's basketball teams managed to defend their titles from Beijing. For the first time since 1936, no U.S. athlete won an Olympic medal in sailing.
Among the nation's medalists were swimmers Missy Franklin, Allison Schmitt and Ryan Lochte, who each won a total of five medals. Swimmer Nathan Adrian and platform diver David Boudia won gold medals in their respective individual events after 24-year-long non-successes. Meanwhile, tennis player Serena Williams followed her sister's success by winning the gold medal in the women's tennis singles event. Gymnast Gabby Douglas became the fourth U.S. female to win a gold medal in the individual all-around event. Allyson Felix became the most successful U.S. track-and-field athlete at the event, winning three gold medals. Swimmer Michael Phelps emerged as the most decorated athlete in Olympic history, with a total of 22 medals won (including four gold and two silver medals in London) – 18 gold, 2 silver and 2 bronze medals – surpassing Larisa Latynina's overall Olympic medal count.
After the disqualification of Russian Ivan Ukhov for doping, Erik Kynard has finally got upgraded from silver to gold, which makes it the 47th US gold medal at these Games, the best American result in terms of gold medals in the Summer Olympics held outside of the United States. Ten years later, Lashinda Demus was promoted to the gold medal as well after another Russian, Natalya Antyukh, was found guilty of doping, bringing the total to 48 gold medals.
Medalists
The following U.S. competitors won medals at the games. In the by discipline sections below, medalists' names are bolded.
| style="text-align:left; width:78%; vertical-align:top;"|
| style="text-align:left; width:22%; vertical-align:top;"|
Competitors
The USOC selected a team of 530 athletes, 261 men and 269 women, to compete in all sports except handball; it was the nation's sixth-largest team sent to the Olympics, but the smallest since 1988. Athletics was the largest team by sport, with a total of 125 competitors.
The U.S. team featured 302 first-time athletes, and 228 returning Olympians to participate in these games. Among the returning Olympians, seven of them had competed at their fifth Olympics (high jumper Amy Acuff, archer Khatuna Lorig, shooters Kimberly Rhode and Emil Milev, indoor volleyballer Danielle Scott-Arruda, and eventing riders Phillip Dutton and Karen O'Connor – the oldest of the team at age 54). Twenty-one athletes made their fourth Olympic appearances, including springboard diver Troy Dumais, track hurdler Angelo Taylor, and beach volleyballers and double-defending champions Kerri Walsh Jennings and Misty May-Treanor. Fifty-seven athletes made their third Olympic appearances, including rifle shooter Matt Emmons, and twins Bob and Mike Bryan in the men's tennis doubles match. One hundred and forty-three athletes were two-time Olympians, including former defending champions Justin Gatlin (athletics) and Anthony Ervin (swimming), who both made their comeback in London after long years of absence. Two hundred and eight returning athletes had competed in Beijing, including 124 Olympic medalists, and 76 defending champions.