Michael Phelps set 39 world records during his career. The total consists of 29 individual records and 10 relay records, making him one of the most dominant record-setters in swimming history.
Most of Phelps's records were set in long-course pools measuring 50 meters, the standard format used at the Olympic Games and major international championships. His records covered events including butterfly, freestyle, and individual medley races, as well as U.S. relay teams. His extraordinary 2008 season was especially productive: he broke seven world records while winning eight gold medals at the Beijing Olympics.
The number 39 refers to records he set over his career, not necessarily records he still holds today. Swimming records are frequently broken as athletes improve, rules change, or relay teams become faster. Phelps's total surpassed Mark Spitz's previously reported record of 33 world records, though historical comparisons can vary depending on which governing body and record categories are counted.