Post Malone fell down a flight of stairs during a recent show in Indiana...but he didn't spill a drop from his red solo cup.

He was walking to greet some fans, when his foot slipped on one of the stairs. Down he went...landing hard on his bottom. A group of security guards rushed to make sure he was okay. Post was fine. He popped right up and walked over to a group of fans who gave him a bouquet of sunflowers. He took a drink from his cup and walked away.