The Quietly Confident Quartet of Australia wins the men's 4 x 100 metre medley relay at the Moscow Olympics, the only time the United States has not won the swimming event at Olympic level.

The Quietly Confident Quartet was the self-given name of the Australian men's 4 × 100 metres medley relay swimming team that won the gold medal at the 1980 Summer Olympics in Moscow. The United States boycotted the Moscow Olympics in protest against the Soviet invasion of Afghanistan and, through the 2016 Olympics, the Australian victory remains the only occasion the United States has not won the event at Olympic level since its inception in 1960. The quartet consisted of backstroker Mark Kerry, breaststroker Peter Evans, butterflyer Mark Tonelli, and freestyler Neil Brooks. The team was nominally led by its oldest member Tonelli, who was 23 and was also a spokesperson for the Australian athletes' campaign for their right to compete at the Olympics against the wishes of the Fraser government. The team was seen as an unlikely prospect to win; all four of the swimmers had clashed with swimming authorities over disciplinary issues and three experienced suspension or expulsion from the Australian team during their careers.

Australia competed at the 1980 Summer Olympics in Moscow, USSR. In partial support of the American-led boycott of the 1980 Summer Olympics, Australia competed under the Olympic Flag. 121 competitors, 93 men and 28 women, took part in 92 events in 17 sports.

The men's 4 × 100 metre medley relay event at the 1980 Summer Olympics was held in Moscow, Soviet Union on 24 July 1980 in the Olympiski Sports Complex. A total of 13 teams participated in the event. These were split over two heats held in the morning of that day, and the eight fastest teams qualified for the finals held in the evening of the same day.

The 1980 Summer Olympics, officially known as the Games of the XXII Olympiad and officially branded as Moscow 1980, were an international multi-sport event held from 19 July to 3 August 1980 in Moscow, Soviet Union, in present-day Russia. The games were the first to be staged in an Eastern Bloc country, as well as the first Olympic Games and only Summer Olympics to be held in a Slavic language-speaking country. They were also the only Summer Olympic Games to be held in a self-proclaimed communist country until the 2008 Summer Olympics held in China. These were the final Olympic Games under the IOC Presidency of Michael Morris, 3rd Baron Killanin before he was succeeded by Juan Antonio Samaranch shortly afterward.