Billie Eilish Dropping Mitchell & Ness NBA Hat Collection with Fanatics, Complex

Billie Eilish is putting her stylish stamp on the NBA -- the singer is giving fans a chance to rock her signature look at games ... by releasing her own team hats!!

TMZ Sports is told the nine-time Grammy winner teamed up with Fanatics and Complex to release some limited-edition Mitchell & Ness lids -- each being decked out in custom Billie Eilish patches to highlight "authenticity, nostalgia and individuality."

The "BIRDS OF A FEATHER" crooner is no stranger to rocking M&N attire -- she loves her throwback jerseys ... and usually accessorizes the threads with a snapback or fitted whenever she hits the stage.

Now, hoop fans can show off their favorite musician and basketball squad at the same time ... with the Lakers, Bulls, Knicks, Cavs, Nets, Bucks, Warriors and more getting exclusive designs.

There's even a Sonics hat, too, for those Seattle fans out there waiting for their beloved squad to come back.

It's yet another cool collab for the brands ... as they recently did a special Takashi Murakami collection for the MLB Tokyo Series, as well as a BLACKPINK "In Your Area" line with MLB and the NBA during the K-pop group's recent tour.