Justin Bieber is among the stars in the house for Game 3 of the World Series ... and even though it's in Los Angeles ... JB is cheering his native country's Blue Jays.

We got video of Justin entering Dodgers Stadium on Monday night ... and it looked like he was there solo with no Hailey in sight.

JB looked cool AF ... decked out in Toronto gear -- not saying much as he was led into the stadium with security nearby.

No doubt there are plenty of other stars there cheering on L.A. ... but for the moment, Justin was the highest profile we've seen. Gallery Launch Gallery Fletcher Greene

The series is tied a game apiece ... so it'll be interesting to see what happens tonight!

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