Gwyneth Paltrow does NOT want Jennifer Lawrence playing mommy to her kids!

In what was almost a SUPER-awkward run-in, Chris Martin's ex and his new lover almost came face-to-face at Martin's Malibu pad, on Thursday as Gwynnie picked up Apple and Moses just before JLaw arrived to hang out with her man.

Paltrow arrived around 6:30 for the hand-off, didn't stay long at the house, packed up the kids and headed back to Brentwood and she literally PASSED Lawrence on PCH!

Our photographer who witnessed the crossing says, "They missed each other by about ten minutes. They would have passed each other in Chris' driveway with the kids and that would have been so awkward. I have a feeling Gwyneth would not have been nice to Jennifer."

Sounds like a run-in is bound to happen at some point ... and we hope we get photos of it!