The Paddy Power advert, costing tens of thousands of pounds, eclipses the previous world record holder which stood at 160ft wide and even dwarfs the Hollywood sign in Los Angeles.
It stands taller than three double-decker London buses stacked on top of each other.The record breaker took three years to design and took a 60 man crew over 1000 hours to build.
Paddy Power said he wanted to celebrate the excitement of the races Hollywood style.
"There's more drama in Cheltenham than the whole of Hollywood combined so it might as well have the sign as well," he said.
"It's simply a bloody big sign and I think it looks great - I'm very proud of it."Cheltenham is the biggest and the best race meeting in the world so we wanted to build a monument to reflect and celebrate that.
"Everyone knows how much the Irish love Cheltenham, so we are delighted to finally have built them a sign to celebrate what many people call the Irish people's second home in true Hollywood style."
World's Biggest Advertising Sign video