Justin Bieber Thumbs Down Shohei Ohtani Home Run at World Series

Justin Bieber's ticked off, and probably exhausted, after that epic Game 3 of the World Series ... and the native Canadian unloaded his frustration on homerun slugging Shohei Ohtani.

Check out the video ... the Grammy winner gave a thumbs down at LA.'s Dodger Stadium as Ohtani rounded the bases after one of his 2 homers. The Dodgers are, of course, playing against Bieber's beloved Toronto Blue Jays in a duel for the ages.

The "Sorry" singer bravely repped his team while rocking a #57 jersey with his name on the back. The name is just a coincidence, though, as #57 actually belongs to Jays pitcher Shane Bieber -- no relation.

In the end, L.A. wound up pulling off the win after 18 innings to go ahead in the 7-game series 2 games to 1.