Before taking team gold this week, Britain had never won an Olympic medal in the event that is essentially the equine equivalent of the gymnastics floor exercise.
Now they boast three after Laura Bechtolsheimer also took bronze with what she called her best ride of the Games, set to a medley from the Disney movie "The Lion King".
Dujardin's victory and Bechtolsheimer's podium finish cap a superb two weeks for Britain at Greenwich Park. British riders won the nation's first team show jumping gold in 60 years on Monday and took silver in eventing last week.
Dressage silver medallist Adelinde Cornelissen of the Netherlands, who rode to variations on Tchaikovsky's Nutcracker, set an Olympic record with her score of 88.196 percent.
But that fell immediately to Dujardin, who scored 90.089 percent with her freestyle. During the team competition, she also picked up Olympic record marks for her grand prix test and the more technically demanding grand prix special.
Dutch journalists questioned Wednesday's placing, citing an error in one of Dujardin's final movements.
British judge Stephen Clarke, one of seven who assessed riders from different points around the ring, said the ground jury saw Dujardin's test as more harmonious than Cornelissen's.
"They ended up very close together," he said. "Maybe one had a little bit more power and the other one had a little bit more harmony and self-carriage. Lots of people will have different opinions but our decision was for the harmony."
Dujardin said Valegro gave his all on Wednesday, although the relatively young horse felt tired to her beforehand.
"It was just pure greenness and tiredness," she said of the mistake. "He's 10 years old and he's given me three amazing rides. I couldn't have asked any more from him and to me he's a very special horse."
Dujardin, who only began competing at the highest levels of dressage last year with Valegro and has had a meteoric rise since, wept and hugged the horse after receiving her medal.
But she had fully regained her characteristic composure when answering questions later. It is this inner calm that makes her a great competitor, according to mentor and team mate Carl Hester.
"I've been crawling on my knees to get here and she's just marching along with the bags," Hester, who finished in fifth place on Wednesday with horse Uthopia, joked before the Games.
Valegro, co-owned by Hester and business partner Roly Luard, is expected to be sold after the Games, as is Uthopia. But, for now, there is a little rest and relaxation on the agenda.
"He's going to come home, have a well-deserved break, go in the field, have a lovely holiday," said Dujardin, who started riding the horse six years ago.
"I guess (whether to sell Valegro) is between Carl and Roly," she said. "And if anything does happen - yeah, God, I'd miss him. He means the world to me. But there's no decision for him to be sold so I'm not going to worry about it."
Earlier this year, she and Valegro set a world record for the highest score in a grand prix special test - a staggering 88.02 percent.
The rise of Hester, Dujardin and Bechtolsheimer has turned Britain from an also-ran nation in dressage to a major force. The three scored the first British gold in the 25-year history of the European Championships last year.
While Bechtolsheimer comes from a privileged background, Dujardin is held up by many as evidence dressage is not the exclusive province of the rich and privileged.
She left school at 16 to train and show ponies her mother picked up cheaply at sales and eventually became a groom.
With an inheritance from her grandmother, she later bought a horse called Fernandez that she trained up in dressage and eventually took to a horse talent day at Hester's.
That day turned out to be pivotal for the double gold medal winner. Hester, recognising her huge potential as a trainer and a rider, offered her a job and gave her the ride on Valegro.
Dujardin attracted as much attention for her attire as her talent this week. She is one of few who opt for a riding helmet over a top hat in the ring, a decision she says she took after fracturing her skull in a fall.
"It's something I do for safety now," she said, adding that she thought this would - and should - become mandatory in the dressage world next year.
- Laura Bechtolsheimer