Moussilmani claimed the top prize over Poland-based Australian Steve Allen, who won last year’s event.
The Lancelin coast became a kaleidoscopic sea of sails, with the kite surfing marathon held at the same time as the windsurfing competition.
The UK’s Olly Bridge claimed the kitesurfing title, while female world windsurfing speed record holder Karin Jaggi, of Switzerland, was the first woman across the line.
Moussilmani, the 31st winner of the marathon, was proud to have won such a renowned event on the competition calender.
“It’s a good start to the year for me and gives me a lot of confidence,” he said.
“I love windsurfing in WA, one of my favourite places in the world… the wind made it a bit hard but such a great race.”
The competition was scheduled to run from Thursday to Sunday, but organisers acknowledged a “dream forecast” for Sunday to create the busiest day in the competition’s 31-year history.