Carrie Underwood Falls Off Stage on Tail End of South Carolina Concert

Carrie Underwood capped off her concert this weekend by belting out tunes in the rain -- but there was an even more dramatic finish as she was exiting the stage ... 'cause she fell.

The singer was the headlining performance Sunday night at the Carolina Country Music Fest in Myrtle Beach -- where she put on one helluva show that ended up getting highlighted by the fact there was a downpour that seemed to come out of nowhere toward the end.

As much of a spectacle as that was ... there was something else that caught fans' attention as Carrie was making her way offstage -- and that would be her going down, seemingly hard. Even crazier is the fact that it was caught on video ... and we got a hold of the footage.

Check it out ... it's a bit of a subtle moment, but if you look closely, you'll see Carrie take a bit of a tumble -- or at the very least, an awkward stumble -- as she starts to descend some stairs toward the back end of the stage.

In a flash, it almost looks like Carrie drops through a hole back there ... either way, her disappearance off the stage doesn't look all that natural -- and something clearly went wrong.

You can even hear people in the crowd scream out that she fell ... so folks certainly noticed.

Now, it appears Carrie addressed the fall -- she posted some photos from her gig this weekend ... and touched on something going awry at the end ... although it's a little cryptic.

She writes, "Well, last night sure was fun! And though the ending was quite unexpected, it made for a night we’ll never forget!" CU attached some emojis touching on rain and weather -- but it's possible she might be quietly referring to the fall at the end.