Selena Gomez may have been singing "Slow Down," but what she did was fall down.

The singer hit the stage in Fairfax, Virginia over the weekend ... literally ... after she accidentally jumped off the main stage during her show and landed on her butt.

The fall happens around the 3:25 mark.

She quickly got back up again, with the help of some front-row fans, but could be heard making a slight scream over the song.

While her mic picked up her startled reaction to falling, her voice was also heard still singing the track -- prompting a ton of YouTube comments saying Selena lip syncs during her concert.

So, what's going on here?

Chances are she was just singing along to a backing track, something very common for pop stars ... especially ones who dance.

What do you think? Sound off below!

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