Visitors to the Big Apple are really sticking it to the city.

Tourists on top of double-decker buses have been slapping their gum wads onto Manhattan street signs as they pass underneath — turning them into a mess of masticated goop.

“The tourists do it,” an employee of TopView, one of the tour companies that operate double-decker buses around the city, told The Post on Tuesday. “They take pictures when they put the gum [on the sign].”

One of the signs that looks as if it’s been dipped in chewed-up bubble gum hangs outside City Hall on Broadway between Murray Street and Park Place, as first noted by an AM New York reporter on Twitter Tuesday.

There is another sign splattered with the sticky substance on Broadway, between Vesey and Barclay streets.

“This close to Ground Zero, that’s disrespectful,” said one NYPD officer working nearby the World Trade Center site about a 10-minute walk away.

“The city knows but it’s New York. Nobody wants to do anything.”

Neither the city Department of Transportation nor the tour bus companies operating double-decker bus tours across the city — TopView, Gray Line and Big Bus Tours New York — immediately responded to requests for comment on the scope of the sticky situation and what they’re doing to address it.

This isn’t the first time New York City has warred with gum wads. In 1939, New Yorkers sticking and spitting their gum in parks and on streets became so problematic that then-Mayor Fiorello LaGuardia warned it was costing the city “literally hundreds of millions of dollar a year to remove.”