Glen Powell and girlfriend Michelle Randolph turned the highly anticipated Texas-Tennessee game into a date ... and we have the pic of them having a blast!

In the photo obtained by TMZ ... Glen -- who sported an orange University of Texas hat and a matching button-down shirt -- beamed at Michelle, who kept it casual in a white tank top and sunglasses.

A witness tells us ... the two were seated in a box inside Neyland Stadium along with friends for Saturday's game in Knoxville.

It was a big game ... even President Trump was in the stands for the big showdown pitting the Tennessee Volunteers against the Texas Longhorns ... and was booed by onlookers at one point.

We bet Glen's smile grew even wider after the match-up ended ... the undefeated Longhorns beat the Volunteers 20-17.

It makes sense we'd see the couple out and about more often ... the actor told TMZ earlier this month that their relationship was "very serious."

The pair became Instagram official back in July ... after several sightings of the twosome locking lips in various cities across the country.