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Adams, 33, added the world title to her Olympic,Commonwealth and European crowns by beating Thailand's Peamwilai Laopeam on Friday.
The English fighter won the 51kg final in Astana by a split decision.
Adams, who has qualified for the Rio Olympics, had previously won silver three times at the World Championships.
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After a cagey opening round, Adams was consistently on the front foot and more aggressive than her Thai opponent.
She rocked Laopeam with a straight right in the second round and, despite being caught with a combination in the third, finished strongly in the fourth round.
"I've finally done it," she said. "And what better year to do it than in the year of the [Olympic] Games? I've cemented my place in history. The champ is here!"
One of the judges scored in favour of Laopeam throughout the fight, but Adams ascribed her hard-earned victory to high-quality preparation and greater desire.
"I stuck to the tactics, listened to the coaches, did all the training and left nothing to chance," she said.
"It was a touch-and-go fight. She's a really good opponent and deserved to be in the final, but I just gave a little bit more and wanted it that much more."
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Great Britain's Nicola Adams completed her full set of international honours with a flyweight gold medal at the AIBA World Championships in Kazakhstan.