The South African made her latest rewrite of history look easy, as she glided home in 2 minutes 24.42 seconds to clip 0.09sec off her previous record.
Heyns' record was her sixth world mark in the past six weeks and the eighth set at this week's championships.
"Sooner or later I'm going to retire and I only have `x' amount of swims left, so I might as well enjoy each one," Heyns said. "With all the world records in the last week, I was getting to a stage where I felt the pressure of having to set another one. That was the focus tonight: to be really relaxed and to enjoy every bit of that race."
Michael Klim, the swimmer of the meet at last year's World Championships, collected his third gold in Sydney by taking the men's blue riband event, the 100m freestyle, in 48.98sec.
Results, Digest, page 25