Caeleb Dressel made history at the FINA World Championships on Saturday and cemented his status as the United States' new superstar in the pool by becoming the first swimmer to win three gold medals in a single session.

Dressel won the men's 50-metre freestyle and 100m butterfly before leading off for the USA's victorious mixed 4x100m freestyle relay team.

The 20-year-old now has six gold medals at the meeting and can tie Michael Phelps' record of seven - set at the 2007 championships in Melbourne - with success in the men's 4x100m medley relay on Sunday.

Dressel came agonisingly close to taking Phelps' 100m fly world record as he won in a time of 49.86secs. That time was just 0.04s shy of Phelps' benchmark and ensured Dressel took gold by a huge margin from Hungarian teenager Kristof Milak (50.62s), as Joseph Schooling and James Guy (both 50.83s) shared bronze.

"A lot of people like to compare. I am not the same person as Michael Phelps," said Dressel. "I just want to keep doing my own thing for this meet and for the future."

Katie Ledecky claimed her 14th world title and fifth at this year's event with another dominant win in the women's 800m freestyle.

There were also gold medals on Saturday for Sarah Sjostrom and Emily Seebohm, who secured respective triumphs in the women's 50m butterfly and 200m backstroke.