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Double Olympic champion Dujardin, on her World Equestrian Games debut, added freestyle gold to her grand prix special title with a score of 92.161%.
"Riding a horse like Valegro gives you so much confidence," said Dujardin, 29.
Meanwhile, British world number one William Fox-Pitt lies second in the eventing contest ahead of Saturday's cross-country test.
Fox-Pitt and Chilli Morning look well-placed to augment a British medal haul which already includes team dressage silver, two individual titles for Dujardin and four paradressage world gold medals.
Dujardin and Valegro were well clear of Germany's Helen Langehanenberg and Damon Hill NRW, who scored 88.286% for their freestyle test, which differs from other dressage competitions in that riders set their routines to music.
"It's my third time riding that test so it's still very new," said Dujardin. "To do what I've done with it is fantastic.
"After London I didn't think it could get much better, but to go to the Europeans in 2013 and come away with two golds and now to come away with another two golds and a team silver, I just couldn't have asked for any more."
Michael Eilberg came eighth on Half Moon Delphi and Carl Hester, Dujardin's mentor, placed 12th on Nip Tuck.
Eventer Fox-Pitt and Chilli Morning impressed to score just 37.5 penalties in their dressage test, but were beaten by Germany's Sandra Auffarth and Opgun Luovo on 35.2.
"It was definitely the best test he's ever done," said Fox-Pitt - individual silver medallist four years ago - of Chilli Morning.
Nicola Wilson is the next British rider in 16th with Annie Clover. GB lie fifth in the team standings, which are also led by Germany.
Two fences have been withdrawn from the cross-country course after intense rain earlier in the week saturated the ground at Haras du Pin, a noted French national stud an hour south of Caen.
"The cross-country course is serious. It's a good track, quite hilly and certainly undulating. Add the soft ground to it and you've got a serious track."
Charlotte Dujardin and Valegro won their first freestyle dressage world title for Great Britain in France.