9:35 AM PT -- Sources with direct knowledge tell TMZ ... Leonardo DiCaprio and Teyana Taylor are not dating, and there's nothing romantic between them at all. We're told Leo is still in a relationship, and he's not with Teyana. This interaction was strictly friendly, we're told.

Leonardo DiCaprio and his costar, Teyana Taylor, were looking pretty damn cozy over the weekend at a pre-Oscars party ... with a lot of touching going on between the two of them.

Check out these videos of the two actors -- who are currently in production for PT Anderson's new indie flick -- hobnobbing Friday night at the WME party here in L.A., where they were seen making contact at a couple different points in the evening.

Specifically ... Leo was seen with his arm wrapped around Teyana's waist as they got close and chit-chatted in private amid all the hustle and bustle of the party going on around them.

Teyana was wearing a fairly revealing outfit, FWIW ... and her lower back was exposed.

There was another moment where they were getting a little flirty -- with Teyana and LD facing each other and TT fixing Leo's ponytail from the back of his baseball cap. This one wasn't PDA, per se, but you can tell Teyana was comfortable doing it ... and ditto for Leo.

Once the hair help was complete, they continued to talk ... and laughed it up as well. No signs of them doing anything more telling than what we can see here, including kissing.

Still, it's pretty eye-opening to see ... especially since Leo is supposed to be dating model Vittoria Ceretti -- who was noticeably absent from this shindig. The last time Leo and Vittoria were spotted together in public was actually recent -- they were out and about in late Feb.

Teyana, of course, is in the middle of a divorce with Iman Shumpert ... which has gotten pretty ugly at times. They share children together, and while Teyana has tried keeping their divorce proceedings private -- much of the drama has surfaced in public court docs.

Of course, the bigger backdrop here is Leo/Tey acting in the same movie of late -- and on its face, it would appear they've gotten close. We've seen tons of footage of them on set, and they seem intricately involved in the script ... 'cause Teyana's shot a lot of scenes with LD.

Whether they're more than just friends, though ... anyone's guess. Clearly, they're comfortable with one another -- comfortable enough to put hands on each other, at least. One last thing .... we know Leo and Teyana left this party separately, for whatever that's worth.

We've reached out to Leo and Teyana's camp ... so far, no word back.

Originally Published -- 8:11 AM PT