MLB Star Shane Bieber Celebrates Smokin' Hot GF's Birthday, 'I Love You!'

MLB All-Star Game MVP Shane Bieber is on one helluva hot streak right now -- not only is he one of the best pitchers in all of baseball ... his girlfriend is insanely attractive!!

The Cleveland Indians ace wished his lady, Kara Kavajecz, a happy birthday on Thursday ... saying "Man ain’t she somethin?! Cheers to this beautiful birthday girl. I love you!"

Biebs and Kara celebrated the big day with a cute little pizza-making date (take note, fellas).

The couple -- who are both UC Santa Barbara alums -- took their romance to social media in December 2017 ... and they've been going strong ever since.

24-year-old Bieber has been crushing it in the league since making his debut with the Tribe in 2018 ... posting a 19-8 record and 4.01 ERA.

As for Kara ... she just turned 21, just graduated college and is dating one of the best players in baseball. So yeah, things are going well for both.

HBD!!