A YouTube user called UFO Lou posted a clip recorded from the NASA "live feed" of the ISS showing an astronaut working on the habitable satellite from outside.
His posting appeared to be both original and digitally enhanced footage which showed the mysterious shape fly past.
He posted: "No idea what this is. I just hit the record button on capture software."
UFOologist Scott C Waring was excited by the image and suggested it could be a "live donut-shaped creature" drifting through space.
He said: "Its recorded from the NASA ISS live internet cam that anyone can watch. This UFO is similar to the UFOs seen during the tether incident from back in 1996. Like those UFOs, this one appears to be the same shape, and moves the same.
Space fairy. To read more and view the video, click here.