The question of whether Chinese swimming ace Ning Zetao could return to dominate the 2020 Tokyo Olympics got a definitive answer on Wednesday when the pride of Zhengzhou, Henan province, officially announced his retirement on his 26th birthday.

"I will say goodbye to the swimming pool in order to start a brand new life," Ning said on Chinese social-media platform Weibo.

"I did not fear the past and I do not fear the future. I'll keep chasing the beauty of life and accept all the regrets. I believe everything has a plan. I want to thank everyone, especially my fans.

"Bless you all. Hope you all can find the most beautiful happiness on your life trajectory. The way to success is never easy. Push yourself and do not settle."

The retirement announcement shocked fans who believed Ning, who became Asia's first world champion in the men's 100m freestyle at the 2015 world championships in Kazan, Russia, still has what it takes to compete against the world's best.

News of his retirement had been viewed over 60 million times within one hour of his post, becoming the most trending topic on Weibo.

Ning's absence from last year's Asian Games in Jakarta was in sharp contrast to his career-changing effort at the 2014 Asiad in South Korea, where he shot to fame after winning four freestyle gold medals.

After Kazan, he became a national favorite in both the sports and entertainment sectors, attracting sponsors, TV producers and even fashion show organizers anxious to connect their brands to him.

However, a series of distractions, highlighted by a feud with the sport's governing body over endorsement deals, prevented Ning from concentrating on training and competition.

He was later expelled from the national team over his disagreement with the governing body.

Ning returned to Henan province in early 2017 to train without much funding or logistical support, but he stayed motivated and proved at the 2017 National Games that he was still the best sprinter in the country, winning two golds.

Now that Ning's swimming career is over, many are wondering if he will pursue a career in entertainment, although he has previously stated that was not an option. Ning told NetEase Sports that he planned to take a break for a while and then head back to school.