The United States' unincorporated territory of Guam competed at the 2012 Summer Olympics in London, held from July 27 to August 12, 2012. This was the territory's seventh consecutive appearance at the Olympics.
Marco Koch is a German competitive swimmer who specializes in breaststroke events. He is a former world record holder in the 200 meter breaststroke.
Benjamin Anthony Aguon Schulte is a Guamanian swimmer. Schulte entered the international stage at 15 years old when he won a silver medal at the 2011 Pacific Games held in New Caledonia. At the 2014 Micronesian Games, Schulte was awarded medals in all 11 of his events, nine of them gold, earning him the nickname 'Micro Phelps'. At the 2015 Pacific Games, he won gold in the 200m and 400m medley, silver in the 100m breaststroke, setting a Games record in the heats that was later broken by the gold medalist in the final, and bronze in the 200m breaststroke. At the 2016 Oceania Swimming Championships, Schulte earned a gold and a silver medal.
Kevin Cordes is an American competitive swimmer who specializes in breaststroke events. He currently represents the Cali Condors which is part of the International Swimming League. Cordes was a member of the 2016 U.S. Men's Olympic Swimming Team. He won gold in the 4 × 100 m medley relay as a member of the preliminary relay, and took 4th place in the Men's 100m Breaststroke at the 2016 Olympic Games. He is the former American record holder in the 50-meter and 100-meter breaststroke.
Nicolas Fink is an American competitive swimmer. He is a five-time world champion in breaststroke events. He is a world record holder in the short course 4×100 meter medley relay and 4×50 meter mixed medley relay. He is the Americas record holder in the short course 50 meter breaststroke, 100 meter breaststroke, and 200 meter breaststroke as well as the American record holder in the long course 50 meter breaststroke. In the 50 meter breaststroke, he won the World Short Course titles in 2021 and 2022 and World Long Course title in 2022. In the 100 meter breaststroke, he is the 2022 World Short Course gold medalist. In the 200 meter breaststroke, he is the 2021 World Short Course gold medalist.
Viktoriya Zeynep Güneş or Viktoria Solntseva is a Ukraine-born Turkish swimmer. She currently represents Energy Standard in the International Swimming League.
Adam George Peaty is an English competitive swimmer who specialises in the breaststroke. He won the gold medal in the 100 metre breaststroke at the 2016 Summer Olympics, the first by a male British swimmer in 24 years, and retained the title at the 2020 Summer Olympics in 2021, the first British swimmer ever to retain an Olympic title. He is also an eight-time World Champion, a sixteen-time European Champion and a four-time Commonwealth Champion. According to FINA itself, Peaty is widely regarded as the dominant breaststroke swimmer of his era, and the most dominant sprint breaststroke swimmer of all time.
The men's 200 metre breaststroke event at the 2016 Summer Olympics took place between 9–10 August at the Olympic Aquatics Stadium.
The women's 100 metre breaststroke event at the 2016 Summer Olympics took place on 7–8 August at the Olympic Aquatics Stadium.
Kazakhstan competed at the 2016 Summer Olympics in Rio de Janeiro, Brazil, from 5 to 21 August 2016. It was the nation's sixth consecutive appearance at the Summer Olympics in the post-Soviet era. The National Olympic Committee of the Republic of Kazakhstan fielded a roster of 104 athletes, 55 men and 49 women, to compete across seventeen different sports at these Games, the smallest Summer Olympic team since the nation's debut in Atlanta 1996. Moreover, Kazakhstan did not send teams in any of the team sports for the first time in twenty years. Track and field accounted for the largest number of athletes on the Kazakh squad, with 25 entries. There was a single competitor each in slalom canoeing, track cycling, fencing, and table tennis.
Anton Mikhailovich Chupkov is a Russian competitive swimmer. He is the European record holder in the long course 200 metre breaststroke and the Russian record holder in the long course 100 metre breaststroke. He formerly held the world record in the long course 200 metre breaststroke. At the 2015 European Games he won four gold medals in individual and relay events. He won the bronze medal in the 200 metre breaststroke at the 2016 Summer Olympics. He won the gold medal in the 200 metre breaststroke at the 2017 and 2019 World Aquatics Championships.
Jessica Vall Montero is a Spanish competitive swimmer and breaststroke specialist. She has a degree in Biomedicine from the Universitat Pompeu Fabra and has worked at Barcelona's Biomedical Research Center. She swims for Club Natació Sant Andreu, where she has trained for over five years with her coach Jordi Jou, ex-elite swimmer also for C.N. Sant Andreu. Besides elite training, she is also working towards her master's degree in Bioethics from the Universidad Católica de Murcia (UCAM).
Cody William Miller is an American competitive swimmer. He is a former world record holder in both the men's 4×50 meter freestyle relay and the mixed 4×50 meter freestyle relay as well as a former American record holder in the long course 100 meter breaststroke and short course 50 meter, 100 meter, and 200 meter breaststroke events. At the 2016 Summer Olympics, he won a bronze medal in the 100 meter breaststroke and a gold medal in the 4×100 meter medley relay, swimming the breaststroke leg of the relay in the final to help achieve a new Olympic record. In 2019, he won the silver medal in the 100 meter breaststroke at the year's Pan American Games. He competes representing DC Trident in the International Swimming League.
Michael Charles Andrew is an American competitive swimmer and an Olympic gold medalist. He was the 2016 world champion in the 100 meter individual medley. At his first Olympic Games, the 2020 Summer Olympics, he won a gold medal and set a world record as part of the 4x100 meter medley relay, placed fourth in the 100 meter breaststroke, fourth in the 50 meter freestyle, and fifth in the 200 meter individual medley. Andrew's swims in 2021 at the 2020 Olympics made him the first swimmer to represent the United States at an Olympic Games in an individual breaststroke event as well as another individual event other than an individual medley in the then-125-year-history of swimming at the Summer Olympics. He has won 78 medals at Swimming World Cup circuits.
Catherine Michelle "Katie" Meili is a former American competitive swimmer, who won a bronze medal at the 2016 Summer Olympics in the 100 meter breaststroke and a gold medal for swimming the preliminary heats of the 4 × 100-meter medley relay. In 2020, Meili joined USA Swimming Board of Directors for a four-year term as their Athlete Representative.
Lillia Camille King is an American swimmer who specializes in breaststroke. She currently represents the Cali Condors, a team that is part of the International Swimming League. At the 2016 Summer Olympics, she won the gold medal in the 100-meter breaststroke competition and also won a gold medal in the 4x100 meter medley relay, in which she swam the breaststroke leg. At the 2020 Summer Olympics, King won a silver medal in the 4x100 meter medley relay for her efforts in the prelims, the silver medal in the 200-meter breaststroke, and the bronze medal in the 100-meter breaststroke. She is the current world record holder in the long course 100-meter breaststroke.
Molly Hannis is an American competition swimmer who specializes in breaststroke events. She currently represents the Cali Condors which is part of the International Swimming League.
Martina Carraro is an Italian swimmer. She competed at the 2020 Summer Olympics, in 100 m breaststroke and 200 m breaststroke. She was European champion in short course in the 100 m breaststroke at the 2019 European Short Course Swimming Championships in Glasgow, Scotland.
Runa Imai is a Japanese swimmer. She qualified for the 2016 Summer Olympics in Rio de Janeiro in the 200 meter individual medley. She swam the 11th best time in the heats and qualified for the semifinals, where she was eliminated with a 15th-place finish.
The women's 100 metre breaststroke event at the 2020 Summer Olympics was held from 25 July to 27 July 2021 at the Tokyo Aquatics Centre. It was the event's fourteenth consecutive appearance, having been held at every edition since 1968.
Russia 
