Native American activist Amanda Blackhorse -- a social justice leader who helped force Washington's NFL team to change its name -- is now calling for the Chiefs to switch their moniker ... and she's urging Rihanna and Patrick Mahomes to join the cause this week.
Blackhorse and other Indigenous advocates have scheduled a protest at State Farm Stadium on Sunday during the Super Bowl ... in an effort to get the ball rolling on ridding K.C. of its longstanding team name.
Blackhorse and other leaders have said it -- as well as the org.'s "Tomahawk Chop" and "Big Drum" traditions -- appropriate their culture ... and they want changes ASAP.
She tells TMZ Sports ... she's hoping Sunday's boycott will raise awareness for the cause, adding that if K.C.'s star QB and the Big Game's halftime show performer pitch in, it could make a big difference.
Of course, Blackhorse was successful in her crusade to get Dan Snyder's team to make changes -- she was a key plaintiff in a lawsuit that helped pave the way for their switch to the "Commanders."
K.C. Chiefs Banning Headdresses & Native American Face Paint At Games
She's now clearly hopeful she can repeat that in Kansas City.
For the Chiefs' part -- they've made changes at Arrowhead Stadium in 2020 in wake of some of the cries ... banning headdresses and Native American-style face paint. They also said at the time they were looking into imposing further restrictions.
The Blackhorse-led protest on Sunday is slated to go down at the stadium in Glendale at 2 PM ... with a flier urging supporters to ban "racist mascots."