Kentucky Derby -- BANS SELFIE STICKS!!!

If you want a "selfie" at the Kentucky Derby, ya better leave your selfie stick at home -- because Churchill Downs has officially BANNED everyone's favorite phone accessory.

It's a pretty big moment for professional sports -- since selfie sticks are super popular right now ... and seem to have a presence at major events all over the world ... from concerts to Super Bowl media day.

As for why Churchill Downs banned the item, reps say the move was in the best interest of both the fans and the horses ... this according to The Courier-Journal.