Simone Biles lost her mind after Chicago won in a thriller on Monday ... celebrating as if she had just won another gold medal!

The Olympic legend was in D.C. to support her man, Jonathan Owens , during his "Monday Night Football" matchup with the Commanders ... and when the defensive back's Bears pulled off the upset with a last-second field goal, she went crazy.

In a suite with Tremaine Edmunds ' fiancée, Biles screamed, jumped up and down, and hugged everyone in her vicinity.

She then captioned the video of her wild celebration appropriately ... writing, "what.a.game." Gallery Launch Gallery Getty

Owens' Bears headed into Maryland as 5.5-point underdogs, but thanks to three turnovers ... they were able to win the matchup, 25-24, as time expired.

Biles seemed to have

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