LeBron James used his day off from the Lakers to support his son, Bronny ... showing up to the teen's USC game decked out in Trojans gear!
The NBA superstar was in total Dad Mode on Thursday night ... rollin' to the Galen Center in downtown Los Angeles to watch SC face off against Arizona State.
The 39-year-old -- wearing a Trojans hoodie and a cardinal and gold cap -- sat next to Savannah in the best seats in the house .