Las Vegas Raiders star lineman Trent Brown found one -- and rocked the hell out of it during pregame warmups before taking on the Indianapolis Colts.

The design is the same one used in Black Lives Matter imagery -- a closed, raised fist.

We know what you're thinking ... no, the facemask is not legal to use during the game -- so Brown swapped it out with a standard facemask by the time the game kicked off.

We've seen wild cut facemasks in the past -- but never one with a political statement weaved into the design!

The facemask looked awesome -- but it didn't provide the spark the Raiders needed ... they ended up getting blown out by the Colts in a 44 to 27 beatdown.