Naomi Osaka stunned world No. 5 Venus Williams in straight sets in the second round of the Hong Kong Open on Wednesday.

It was No. 64 Osaka's first victory over the former top-ranked 37-year-old Williams, who had won their only past meeting at Wimbledon this year in the round of 32.

Osaka, unseeded at the tournament at Hong Kong's Victoria Park, reached the quarterfinals by eliminating the American second seed 7-5, 6-2 in 1 hour, 24 minutes.

The 19-year-old rising Japanese star scalped yet another giant in women's tennis, following her upset of No. 6 and then defending champion Angelique Kerber at the U.S. Open.

Osaka described the win over seven-time Grand Slam winner Williams as a dream come true.

"Today I accomplished one of my dreams," Osaka said through her Twitter account.

Osaka capitalized on Williams' seven double faults -- six of which came in a disastrous second set -- and converted five of 10 break points.

In the last eight, Osaka will face Anastasia Pavlyuchenkova, who beat Jacqueline Cako 7-6(3), 6-1.