Madonna Threatens Fans Over Cigarettes -- If You Smoke, I'll CANCEL My Concert!!!

Madonna made a serious threat to a bunch of her cigarette-smoking fans in Chile last night ... PUT OUT YOUR BUTTS ... OR I'M NOT GONNA PERFORM!!

It all went down during a sound check for her concert at an open-air theater in Santiago ... when some secondhand smoke blew up in Madge's face ... so Madge blew up on the smokers.

"There are people smoking right now, " the singer lashed out ... "No smoking!"

"If you're going to smoke cigarettes, I'm not doing a show."

She continued, "You don't care about me? I don't care about you. All right? Are we going to play that game? I'm not kidding. I can't sing if you smoke .. Entiendes?"

"You're looking right at me and smoking cigarettes, like I'm a stupid f**king idiot."

In the end, the smoke-aholics extinguished their ciggies ... and Madge went on to perform a bunch of her hits, including the song "Human Nature."