Sharing photos and videos from the sideline, Matthews showed off her Chiefs-red dress as she supported Mahomes.
Mahomes, a quarterback for the Chiefs, and Matthews, both 24, have been together for years. They met in high school while attending Whitehouse High School in Whitehouse, Texas.
Matthews — who owns her own fitness company, Brittany Lynne Fitness— shared numerous photos from Florida leading up to kick off on Sunday, all while repping Chiefs gear.
Wrote Matthews on one Instagram post, “Ready to take home this W!”
She also posted a photo hanging out with Mahomes’ younger brother Jackson Mahomes, writing, “It’s LIV.”
The 49ers and the Chiefs are facing off at Super Bowl LIV on Sunday in Miami at the Hard Rock Stadium. The game is airing on FOX.