Ariana Grande -- My Ass Is a Seahawks Fan

She may be from Florida, but Ariana Grande put her butt on the line for the Seattle Seahawks last night.

The 21-year-old was invited to the sing the National Anthem at the NFL season opener in Seattle ... but before she hit the field, Grande made sure to snap a few sexy selfies to share with the world.

We're guessing Russell Wilson approves.