An "exceptionally rare" two-headed copperhead snake has been discovered in a backyard in the United States.

It was one of very few such creatures found by the public, according to a reptile expert who examined the snake after a resident of Woodbridge, Virginia notified a local animal control business about the find.

Herpetologist John Kleopfer said "bicephalic", meaning two-headed, snakes were rarely seen in the wild because of their short life expectancies.

"[There are] too many challenges living day to day with two heads," Mr Kleopfer wrote on Facebook.

"We were able to determine that the left head has the dominant oesophagus and the right head has the more developed throat for eating."

A photo of the snake was initially sent to Virginia Wildlife Management and Control, who posted it on Facebook.

"Hey y'all, check out these extremely rare photos of an actual two-headed copperhead, that was found in someone's yard in Woodbridge, Virginia, and sent to our Facebook page, this evening!... Cool huh?" the post read.

The internet also thought it was cool, with images of the snake reaching screens around the globe.

But not everyone was a fan.

"Only good snake is a dead one. I would kill it," someone commented on the post.

"This is what nightmares are made of," wrote another.

The snake could soon become an exhibit at a zoological facility, according to Mr Kleopfer.