Denny's Beer Barrel Pub, in Clearfield, Pennsylvania, already had the title with a 6lb burger.
But owners thought a 15-pound burger would prove an even bigger attraction, reports the Pittsburgh Post-Gazette.
Diners who can finish the £25 burger in under five hours win £200, a T-shirt and have their name posted on the pub's wall of fame.
They also get the burger for free.
"Every restaurant needs a gimmick - ours is big burgers," said Dennis Liegey III, son of the restaurant's owner.
Visitors come from as far away as Australia and California just to see the 6-pounders and try to eat them.
The new burger, dubbed the Beer Barrel Belly Buster, is as big around as the inside of a car tyre.
It comes with a cup and half each of mayonnaise, mustard and ketchup, a head of lettuce, two onions, three tomatoes and 25 slices of cheese.
