Four-time Paralympic champion Ellie Simmonds was one of four British winners on day one of the IPC World Swimming Championships in Montreal.
Simmonds, 18, won the women's S6 400m freestyle in five minutes 24.02 secs, 20 seconds ahead of Mexico's Vianney Trejo Delgadillo.
Josef Craig and Jessica-Jane Applegate set world records to win their S7 400m and S14 200m freestyle races.
Steph Millward won S9 100m freestyle gold ahead of team-mate Amy Marren.
For Simmonds and Craig, the performances were repeats of their Paralympic victories at the London 2012 Games.
Both won the 400m, with Simmonds also adding gold in the 200m medley.
Simmonds, whose main rival Victoria Arlen was stopped from competing after the IPC ruled she did not have a permanent disability, is bidding for a further five medals in Canada.
"The 400m free in London last year against Victoria was an exciting race but this one was just me really, which is different," she told BBC Sport.
"You push yourself and your own ability. I'm looking forward to my other events. I have a busy schedule but I will go out and focus on myself."
"I was still really nervous. I felt less pressure than London - London being a home Games and a Paralympics - but I'm a racer: I'm born to race."
Craig broke his own world record to win by 0.05 seconds in 4:39.14 ahead of Russia's Andrey Gladkov, with fellow Briton Jonathan Fox taking the bronze in 4:44.46.
"I'm very pleased, but that's my first race of four in this competition, so I can't rest on my laurels," said Craig, the 2012 BBC Young Sports Personality of the Year.
"I was expecting a PB because I've been training hard, but I never expected it would be that close. Andrey did an amazing swim and kept me on my toes but in the last 50 metres I wanted it to be my title and I just got ahead of him."
Applegate, 16, also emulated her London triumph with gold thanks to a strong second half to her race.
The Norwich-based swimmer was fourth at the halfway mark but stormed through to win in a new world record of 2:09.88, beating the 2:11.47 she clocked in Sheffield earlier this year.
"That was definitely a tough race," she said. "I really had to dig deep in that last length.
"I could see someone out in an outside lane who was going out fast but I had to try and not get too far behind. I was dying a bit on those last 50 but obviously had enough to hold on."
Millward, who got married earlier this summer and is now based in Bath after a spell at Swansea, was thrilled with her first world long course gold medal after winning silvers and bronzes both at the last Worlds in Eindhoven in 2010 and at last summer's Paralympics.
"That was absolutely amazing," she said after finishing 0.41 seconds ahead of teenager Marren, who won her first major international medal.
"I would never have dreamed myself to be a freestyle swimmer, but now I'm world champion. It's crazy. It's probably my third stroke behind backstroke and butterfly.
"I wanted to come back to freestyle after not competing it at the Paralympics and I've been doing more training with my new squad, Aquae Sulis."
Fellow Briton Susie Rodgers set a season's best to take silver in the women's S7 400 freestyle final, while there was also a silver for Hannah Russell in the S12 100 free final.
Ollie Hynd, who won Paralympic gold in the SM8 200m medley, set a British record as he claimed bronze in the S8 100 backstroke.
There was also a bronze for Andrew Mullen in the S5 50m butterfly.