World No.1 Naomi Osaka has joined the Nike roster of athletes.

The announcement came just hours after Osaka was a guest as the LA Lakers took on the Golden State Warriors - and was spotted chatting to injured superstar LeBron James, another Nike athlete.

The pair had met previously, just after Osaka's triumph at the US Open. 

READ: 'It still feels surreal' - US Open champ Osaka makes the media rounds

"Naomi is an incredible talent to add to our roster and help drive our commitment to inspiring a new generation of female athletes," said Amy Montagne, Nike's VP, GM of Global Categories. "We are thrilled to have her join our team."

Osaka is a two-time Grand Slam champion, and the first Japanese player to reach the No.1 spot.

The 21-year-old said she was "proud" to sign the deal, which begins this week; her first tournament in Nike gear will be the Porsche Tennis Grand Prix in Stuttgart, starting on April 22.