A 16-year-old schoolgirl was stunned to spot a mysterious black circle in the sky over Leamington Spa on Friday.
Georgina Heap was playing tennis with her mum Jo when she saw the black halo UFO.
She said the huge ring floated in the sky for three minutes before disappearing completely.
Speaking to the Daily Star, the teenager said it was "the weirdest thing I have ever seen".
Georgina added: "It was just floating there like a cloud and then it disappeared. It wasn't birds either.
"There were about ten of us who stopped what we were doing and watched.
UFO expert, Nick Pope, described the video as "truly bizarre" and ruled out it being a smoke ring.
Speaking to the Huffington Post, he said: "One other possibility is that the shape is made up of millions of bees or other insects, but I've never heard of insects behaving in this way before, so if this is the explanation, it's a real-life X-File."
Warwickshire Fire and Rescue Service said there were no reports of fires around that time and the Met Office said it did not believe the ring was weather-related.
Earlier this month, a UFO was spotted approaching a deer in rural Mississippi, USA by a couple who had set up trail cameras in the woods.
Edith and Rainer Shattles told WLOX they were hoping to capture images of bucks and fawns but instead discovered mysterious lights in the night sky over the Cumbest Bluff part of Jackson County.
Edith said: "We have unusual things happen around here that happen, but it's usually associated with our grandchildren. But this case, we didn't know what it was.
"I was looking for a nice buck to be showing up on the trail camera actually."
The 30-minute footage showed a dim light emerging from the darkness and getting brighter a few minutes later. A weird shape then appeared on the camera before the deer were lit up brightly. Soon another sharper light appeared and got closer, seeming to focus on the deer.