Swimming has been a foundational sport at every modern Summer Olympics, opening its events to women since 1912 and now boasting the second-highest number of medal contests after athletics. Initially, early competitions from 1896 to 1906 took place in open water venues like the Mediterranean Sea or the Seine, before the introduction of a 100-meter pool in 1908 and the standardized 50-meter pool with marked lanes by the 1924 Games. Significant advancements like electrical timing in 1912, diving blocks in 1936, and the separation of the butterfly stroke as its own event in 1956 have continually shaped the sport.
Over the decades, Olympic swimming has expanded its program and improved gender equality, introducing medley relays for both men and women in 1960 and the 10 km open water marathon in 2008. Notably, the 2020 Games added the women's 1500m and men's 800m freestyle events, alongside the mixed 4x100m medley relay, evening out long-distance opportunities. Athletes' times have consistently decreased, attributed to better training techniques, evolving swimwear, and innovations in pool design, which now incorporate features to reduce drag and enhance speed.