Peaty won the event in 2015 and 2017, and the 24-year-old finished first in a time of 26.06 seconds - falling just short of his own world record set in Budapest two years ago (25.95secs).
Felipe Lima finished in second place, 0.6 of a second slower, while Joao Gomes snatched bronze in 26.69.
Silver medallist Brazil's Felipe Lima (L), gold medallist Britain's Adam Peaty (C) and Bronze medallist Brazil's Joao Gomes Junior pose with their medals after the final of the men's 50m breaststroke event
Image credit: Getty Images
The Brit won gold in the 100m earlier this week, and Peaty's success extends his impressive unbeaten record in five years at the breaststroke.
Remarkably, he has won both the 50m and 100m breaststroke titles at the past three World Championships (2019, 2017 and 2015).
Meanwhile, Britain also celebrated bronze in the mixed 4x100m medley relay as Australia took gold with the United States in second.