The startling 8kg spud was discovered by farmers Marli and Paulo Ciquinel in the town of Meleiro in the southern Brazilian state of Santa Cantarina.
Photos show how the huge potato has grown to resemble a human foot, complete with toes that descend in height order.
The largest of the ‘toes’ is covered in roots that look like hair and the “foot” reaches up to nearly knee-height.
The mutant-looking potato appears to have one extra toe.
The couple planted the potato in the vegetable patch behind their home where they also grow other vegetables.
Marli told reporters: “We have never seen anything like it. Let’s see what we are going to do with the potato.
Perhaps, we can put it on display if anyone would like to see it.
“I was a little bit scared when we harvested that potato.”
The couple normally only plant vegetables for their own consumption but the couple do not expect to eat the potato.
Marli and her husband are retired and told reporters they have been planting potatoes behind their home for six years.