Swarm of Potential UFOs Spotted in Sky Above Chino Hills, CA

We may have another UFO sighting on our hands -- and this one sure seems legit, seeing how there's no explanation for what the heck all these lights in the sky are.

Check out this wild video obtained by TMZ, which appears to show multiple giant orbs in the heavens above Chino Hills, CA -- circling each other and moving in strange, eccentric patterns ... with no light source coming from down below, per an eyewitness, anyway.

We're told this was shot a couple days ago, on Dec. 9, around 9 PM. The woman who filmed it tells us her grandson was taking the trash out, when he looked up and saw this ... which prompted the rest of the family to come out and take it all in.

The witness says she thought there was a grand opening happening, but they couldn't trace any such event nearby ... and as they mention on camera, there's no beam coming from down below. Seems the lights are really up there, generated by something in the clouds.

The crazy part is, we're told that after about 30-40 mins ... these things completely disappeared, without a trace.

There doesn't seem to be any explanation that we could find for what we're seeing here -- it's a mystery. Of course, one answer could be ... this is a UFO. Or lots of them, more like. One might even call them a fleet -- which is what one pilot recently says he saw as he was flying high above civilization himself.