The swimming competitions at the 2004 Summer Olympics in Athens took place from 14 to 21 August 2004 at the Athens Olympic Aquatic Centre in Marousi. It featured 32 events, a total of 937 swimmers from 152 nations, and the program's changes instituted in the previous Games, including notably the three-phase format for all short-distance races.

David Michael Rhys Davies is a Welsh former competitive swimmer who has represented Wales at the Commonwealth Games, and swam for Great Britain at Olympic, World and European level He is the 2006 Commonwealth Games champion at 1500 metres freestyle and holds the rare distinction of having won medals in all six major long-course and short-course international championships available to him.