Robert De Niro popped up to personally thank Upper West Side firefighters who extinguished the blaze at his Central Park West apartment that’s left him homeless. He hung with the FDNY guys for hours Friday, and even ordered them a giant catered lunch.

Spies say De Niro and his wife, Grace Hightower, were seen arriving to personally thank Engine Company 23 for putting out the fire in their luxury apartment after their clothes dryer ignited in June and spread flames through the ultra-posh pad.

The pair stayed at the West 58th Street firehouse for two hours, spies told Page Six. “De Niro took pictures with the guys, and got a full tour of the firehouse,” a source said, adding that the actor — who appeared in Ron Howard’s 1991 firehouse drama “Backdraft” with Kurt Russell — also treated the FDNY crew to lunch by ordering grub from his downtown restaurant Tribeca Grill.

“The food was a huge spread with two servers, meatballs, eggplant sandwiches and more,” our spy added. A source close to the star told us it was initially Hightower’s idea to stop by the station and say thanks.

The night before the surprise visit, De Niro was in Las Vegas, spies say, with Michael Douglas, Morgan Freeman and Kevin Kline. The group was beginning rehearsals for “National Treasure” director Jon Turteltaub’s bachelor party movie “Last Vegas,” about a group of guys in their 60s who throw a wild bash for their one remaining single friend before he finally ties the knot.

And last night, busy De Niro won the best supporting actor honor at the 16th Annual Hollywood Film Awards at the Beverly Hilton for his role in “Silver Linings Playbook” as Bradley Cooper’s Philadelphia Eagles-obsessed father. Cooper won for best actor, and De Niro’s been getting big Oscar buzz.

Page Six reported last week that the star and Hightower are still looking for a suitable crash pad in New York while making renovations to their apartment, which could take up to three years due to the fire.