Kathleen Genevieve Ledecky is an American competitive swimmer. She has won seven Olympic gold medals and 21 world championship gold medals, the most in history for a female swimmer. She has won a world record 16 individual gold medals at the World Aquatics Championships. Ledecky's six individual gold medals at the Olympics and 26 overall medals at the World Aquatics Championships are records in women's swimming‌. Ledecky is the world record holder in the women's 800- and 1500-meter freestyle as well as the former world record holder in the women's 400-meter freestyle. She also holds the fastest-ever times in the women's 500-, 1000-, and 1650-yard freestyle events. She is widely regarded as the greatest female swimmer of all time and one of the greatest Olympians of all time.

Swimming is an individual or team racing sport that requires the use of one's entire body to move through water. The sport takes place in pools or open water. Competitive swimming is one of the most popular Olympic sports, with varied distance events in butterfly, backstroke, breaststroke, freestyle, and individual medley. In addition to these individual events, four swimmers can take part in either a freestyle or medley relay. A medley relay consists of four swimmers who will each swim a different stroke, ordered as backstroke, breaststroke, butterfly and freestyle.