The snap of the small "being" was taken in the Parque Forest in Santiago, Chile, by civil engineer Germán Pereira, who could not believe what he caught on camera as he photographed police officers on horse back.
UFO hunters claim the picture "clearly shows a small humanoid" strolling across the road behind the mounted police.
Mr Pereira said: "I thought it would be interesting to photograph a group of Carabineros (state police) on horseback patrolling the sector.
"The photo was taken at 5.40pm approximately from the corner of JM de la Barra and Av Cardenal José María Caro, in front of bellas Bellas Artes and looking east."
He said due to overcast conditions he had the camera on a low speed and with an optical zoom of times ten, which made the image blur.
He added: "The fact is that I am very impressed by this image. I attest to the fact that it is not a fraud nor anything similar.
"For this reason I have made it public.