A video uploaded to conspiracy YouTube channel The Hidden Underbelly shows what appears to be a bright light lifting from the ground in the hills in the background.
The light then moves towards the camera slowly, before veering off to the left of the screen.
Viewers of the video were convinced that the bright light is definitely a UFO, and believe that the authorities have some answering to do.
Somme Bomb posted: “Would love to see them explain that one. You can see clearly the light interferes with the clouds and you can see the reflection in the river.”
Twilights daughter added: “They must have been checking out the geysers and scenery just like the humans were.”
Yellowstone has also piqued the interest of many around the globe over fears that it could soon erupt.
The Yellowstone Caldera supervolcano last erupted 70,000 years ago but a spike in seismic activity around the national park has unsettled nerves.
If the Wyoming volcano were to erupt it would kill an estimated 87,000 people immediately and make two-thirds of the USA immediately uninhabitable.
The large spew of ash into the atmosphere would block out sunlight and directly affect life beneath it creating a “nuclear winter”.
The massive eruption could be a staggering 6,000 times as powerful as the one from Washington’s Mount St Helens in 1980 which killed 57 people and deposited ash in 11 different states and five Canadian provinces.
If the volcano explodes, a climate shift would ensue as the volcano would spew massive amounts of sulphur dioxide into the atmosphere, which can form a sulphur aerosol that reflects and absorbs sunlight.