Anyone leave a chainsaw on the train?

That’s just one of the bizarre items waiting to be reunited with its owner at the Long Island Rail Road’s new lost-and-found office.

LIRR officials on Tuesday unveiled the 1,100-square-foot office — located in Penn Station below the Amtrak concourse — along with some of the unusual items it contains, including a violin and a karaoke machine.

The facility, which processes over 20,000 items each year, is open to LIRR riders who have lost items anywhere in the system — from Penn Station to Montauk.

Unclaimed items eventually get sold off to an outside vendor, but the railroad keeps them from anywhere between three months and five years, depending on their value.

Electronics, like phones and computers, are the most common lost items, along with gloves, umbrellas and backpacks.

But Terminal Manager Steve Terracciano said he’s seen everything from a prosthetic leg to medical marijuana — which was immediately reported to the police.

“We’ve had engagement rings — things that are very near and dear to people’s hearts,” he said.

Riders can fill out lost item forms online or in person. If an item is located, it can be picked up in person or the LIRR can arrange a FedEx delivery, which is billed to the rider. Terracciano said he’s returned items to as far as Australia.

Metro-North riders can find their lost items at Grand Central. The bus and subway lost-and-found is also located at Penn Station.

Terracciano stressed the importance of riders providing as much details as possible.

“They’ll come in and fill out an inquiry form, but they’ll [only say], ‘black knapsack,'” he said. “That doesn’t narrow it down. Ninety percent of my knapsacks are black.”