As we previously reported, the young power couple has been dating since early 2019 ... and are still still going strong during the pandemic.

While regular folks aren't allowed to be in attendance for the Open, 23-year-old Cordae was given the green light as Naomi's guest ... so he was able to be a supportive BF for her semifinal match against Jennifer Brady.

Cordae wasn't just a wallflower, either ... the "Gifted" MC was seen pumping his fist and getting as passionate as you can for a tennis match.

Not like 22-year-old Naomi needed any luck -- she's the 9th-ranked player in the world -- but Cordae's presence didn't hurt ... as she beat Brady 7-6 (1), 3-6, 6-3 to reach Saturday's final against Victoria Azarenka.

Osaka's been on a tear recently ... and sending a powerful message in the process by honoring victims of violence and police brutality like Ahmaud Arbery and Breonna Taylor on her masks.

As for Cordae ... you'll recall the dude used to have 3 letters before his name. But, for those late to the game, the YBN collective is no more.