Ning, who won both 50m and 100m free golds at the 2014 Asian Games, was the first Asian swimmer to make the men's 100m free final at worlds since 1973.

"Just getting to the final was a big achievement. I didn't even think about a medal. When I touched the wall I didn't realize I had won," said Ning.

Australian star Cameron McEvoy, who produced the fastest time in the semifinals, had to settle for silver in 47.95 and Argentina's Federico Grabich took the bronze in 48.12. Olympic champion Nathan Adrian of the United States only finished seventh in 48.31.

Ning's lethal weapon is second-half sprint which played a key role tonight. He closely followed Canadian Santo Condorelli at the 50m mark and made a strong sprint in the last meters.

Ning started swimming at the age of eight in a bid to improve his health only. But his quick learning of different strokes and techniques attracted the attention of local coach Guo Hongyan.

At the beginning, Ning's specialty was breaststroke and he had focused on individual medley for many years. But a chronic bone calcification in his right knee forced him to switch to short distance freestyle later.

In 2011, Ning suffered a heavy blow when he was suspended one year after testing positive for clenbuterol.

Ning overcame the incident and came back strongly after he served out the suspension. In 2014, he was awarded the Best Male Athlete of the Year by CCTV Sports Award thanks to his stellar performance in the Incheon Asian Games.

Now, Ning is eyeing the Rio Olympics. "Now I can think about the Rio Olympic Games," he said. "I hope I can achieve good results in Rio."