Spain's Carolina Marin became the first woman to win three singles titles at the World Badminton Championships with victory over India's PV Sindhu.
The 25-year-old seventh seed won 21-19 21-10 in Nanjing, China, to add to her 2014 and 2015 titles.
It was a repeat of the 2016 Olympic final, which Marin also won.
World number three Sindhu, 23, was runner-up at the World Championships in Glasgow last year and the Commonwealth Games in Australia earlier this year.
Elsewhere, Kento Momota beat China's Shi Yuqi 21-11 21-13 to become the first Japanese man to win the world title.
Momota dedicated his win to those who supported him after he was banned from playing for his country for visiting a casino in 2016.
"There was a time when I was away," he said. "But I got a lot of help and support from many people. This title is a good reward for them."