Katy Perry & Russell Brand -- Ignore Each Other at Lakers Game

Trying not to make eye contact, former couple Katy Perry and Russell Brand sat on opposite sides of the court at the Lakers game at Staples Center in L.A. on Tuesday.

Both Katy and Russell -- who divorced earlier this year -- employed one of the hardest acting techniques known to man ... pretending it's not awkward when you run into your ex.

At least they can agree on which team to root for.