A top dinosaur hunter says he's found a real Tyrannosaurus Rex footprint in an American desert where the monsters lived millions of years ago.
Dr Phil Manning discovered the massive 76cm-long footprint in a place called Hell Creek, in the middle of a scorching hot desert in Montana.
The dusty print is now being glued together so it can be lifted out of the ground and studied by scientists.
They want to see if it really does belong to the king of the dinosaurs.
Eventually it is hoped the print will go on display in an American museum so people can see it for themselves.
The T Rex is one of the world's most famous dinosaurs and loads of bones and fossils from the fearsome creature have been unearthed in Hell Creek in the past.
But, if Dr Manning's suspicions are right, he will have discovered the world's first T Rex footprint.
He said the footprint was that of a very, very big dinosaur.
"People have been trying to find these tracks for over 100 years and these are really quite special because they put the animal at the scene of the crime," he said.
"A live animal leaves tracks - bones can be transported after death, so it really puts the animal in the context of where it used to live."