Taylor Swift likes her workouts solo -- as in no one else can be in the gym when she sweats -- even if that certain someone else is Justin Bieber.
Here's the deal ... Justin was at Dogpound Gym in West Hollywood with a bunch of people, and everything was chill until Taylor and her crew rolled up.
We're told everyone -- including JB was asked to get the heck out of the gym -- because Taylor wanted it to herself. Justin's security team was approached and asked to leave, but JB's team held firm and said he was going to finish his workout before taking off.