Lil Nas X trumped Mickey Mouse Saturday, by crashing a wedding reception at Disney World, and some of the guests fully melted down!

The “Old Town Road” icon apparently schemed with the bride, because the 2 of them walked into the reception hall and guests as his song filled the room … and guests were shocked.

You hear one woman scream, “What the f*** is happening right now!?!!”

The 20-year-old rapper hit the dance floor and no doubt about it … it made the wedding a night to remember.

Lil Nas X has reason to celebrate … he snagged an NAACP Image Award Saturday night for Outstanding New Artist. And, as you know, he also won 2 Grammys for “Old Town Road.”