Two records were set within minutes of each other in the semifinals of the 100-meter butterfly.
Phelps, 18, swam the second semifinal in a blistering 51.47 seconds. His effort came minutes after Andrii Serdinov of Russia posted a 51.76, which was .05 seconds faster than the record Australia's Michael Klim set in 1999.
Within an hour, Phelps grabbed the 200-meter individual medley gold medal and obliterated his rivals.
Phelps left standouts like Australian superstar Ian Thorpe, Massimiliano Rosolini of Italy and Jani Sievinen of Finland in awe.
Thorpe, known as, "The Thorpedo," Thorpe was beaten by more than 3.5 seconds.
Finland's Hanna-Maria Seppala won gold in the 100 freestyle and Aaron Peirsol captured gold in the 200 backstroke.