An eyewitness shot these photos last Saturday while heading south on the 101 Freeway, just outside of Thousand Oaks as she was approaching Westlake Village around sunset. We're told she was on her phone when she saw this thing hovering in the sky, flying in the same direction she was heading ... with a group of lights trailing behind it.

The eyewitness says she shot three consecutive photos as quickly as she could, and as you can see ... the unidentified object appears to have changed positions, both tilting ever so slightly and moving to a new spot in the sky. We're told this UFO was only visible for a few seconds, before it literally vanished into thin air. We know ... far-fetched, right?

That's what we thought too -- but we've been assured these photos are NOT altered, and they show what they show. We were skeptical -- thinking these could've been tweaked in Photoshop -- so we had one of our art gurus take a closer look to see what she thought.

Turns out, our own photoshop wiz seems to agree ... these don't look like fakes.

Our graphic artist tried an experiment with stock images of "glowing discs," "UFO's" and "flying saucers" ... to see if the images could be manipulated in a similar fashion as the tipster's photos. She concluded it would be hard to cut/paste these images with the exact angles of the tipster's images. So, these photos do appear to be legit ... or at the very least, probably not photoshopped.

We also reverse image searched these pics, BTW, and couldn't track down ANY that were exactly the same -- so again, it lends credence to the idea these were taken on the spot, without being doctored after the fact.

So, where does that lead us in the end??? Welp, depends on what you want to believe. On its face, this looks to be a straight-up UFO sighting. IF that is in fact the case -- who woulda thought Hollywood had it right all along in its depictions?!?