Major drama at the "Don't Worry Darling" premiere -- and we're not even talking about Olivia Wilde and Florence Pugh ... this one's all Harry Styles and Chris Pine, with an apparent spit attack.

The internet is fiercely debating whether HS hocked one onto CP's lap right before the film started playing at the Venice Film Festival Monday ... and people are torn.

Watch the video ... you see Harry walk up to his seat -- which is sandwiched between costars Chris and Gemma Chan -- and just as he's about to plop down, he appears to somewhat bend forward and purse his lips in a spitting fashion. It's all very fast and smooth.

From the clip alone, it's difficult to say with certainty he actually spit or not -- but Chris' reaction certainly seems to suggest he, at the very least, thought he might've been spit on.

The dude pauses and looks down at his leg/his seat -- and also stops his clap completely -- only to look up in what appears to be comical disbelief that this just happened (or didn't?) Harry carries on as if nothing's amiss -- so the jury's still out on whether he did it or not.

There are a couple different angles of the "spit shot" ... and in some, it looks more clear than others, which could work in Harry's favor. However, one video of Chris standing up and applauding -- presumably after the credits rolled -- show him seeming a little tense.

We've reached out to Chris and Harry's reps for clarification, but no word back just yet. Neither star has addressed it either on their own at this point ... so for now, it's just speculation on Twitter.