The internet is gagging over a teaser for the new season of "Euphoria" ... and not in a good way.

Sydney Sweeney -- who plays Cassie -- is seen in a jaw-dropping scene dressed like a literal baby, complete with a pacifier ... and fans seem to think it's pretty creepy. In fact, viewers are questioning how the show went from an edgy drama to what some are calling "full-blown nightmare fuel."

The scene reportedly ties into a wild new storyline where Cassie is creating adult content on OnlyFans while dressed as an infant.

For the aberration, fans are dragging creator Sam Levinson as well as Sydney for going there.

"Sydney girl, you can say no to scenes," one wrote.

"They did Cassie dirty," wrote another.

Of course, controversy is nothing new for Euphoria, which has built its brand on pushing boundaries ... but this might be the moment even diehard fans are saying it went too far.

Season 3 premieres tonight ... and it's already bonkers.