Lil Yachty had a lil bit of a mishap ... taking a full-on tumble off the stage while opening for Tyler, the Creator's "Chromakopia" tour.

Check out the clip -- Yachty was working the stage at Milwaukee's Fiserv Forum Thursday when he hit a little turbulence ... stumbling at the edge before making a panicked leap, clearly choosing the less painful crash landing!

Nonetheless, he still hit the floor hard -- but like a true pro, he shook it off and kept it moving.

Eyewitnesses tell TMZ he was totally fine and powered through the performance ... though they couldn’t say the same for the sound quality, which they dubbed "trash."

Yachty did take a brief pause after the fall, yelling to the crowd, "WTF, I almost died!" before hustling back on stage -- because, of course, the show must go on!