Masse's gold was Canada's first of the championships.
On top of winning gold and becoming the first female Canadian World Champion in swimming, she also just broke a world record, with a time of 58.10 seconds in the 100-metre backstroke.
Masse finished the race in 58.10 seconds, breaking the mark set by Great Britain's Gemma Spofforth (58.12 seconds) at the 2009 FINA World Championships.
Canada's gold medal winner Kylie Jacqueline Masse is flanked by United States' silver medal winner Kathleen Baker, left, and Australia's gold medal winner Emily Seebohm, right, during the ceremony for the women's 100-meter backstroke final during the swimming competitions of the World Aquatics Championships in Budapest, Hungary, Tuesday, July 25, 2017.
Masse has now won a medal in the 100-meter back in consecutive summers, as she took bronze at the Summer Olympics in Rio past year.
She will compete in the 200-metre breaststroke later this week.