Mayor de Blasio is so desperate to gin up support for his going-nowhere 2020 presidential run, he’s now spewing blatant falsehoods about his performance as mayor — figuring, perhaps, that non-New Yorkers won’t notice.

As a service to readers, we’ll set the record straight.

Falsehood No. 1: “I’m proud to say in New York, we’ve divested $5 billion” in pension-fund assets “from the fossil-fuel industry,” Hizzoner bragged in Iowa.

Uh, no. As Politico noted, the city’s pension funds have divested exactly zero from fossil-fuel companies.

Yes, there are plans to study the idea, but no such study has even begun. And even if, at some point, the pension funds do divest, de Blasio won’t be able to take credit because he doesn’t control their boards.

Falsehood No. 2: The mayor claims Gotham is set to pass a bill this year requiring most businesses to offer “two weeks paid vacation” to “every working person.”

Sorry, Mr. Mayor. Corey Johnson, speaker of the City Council (which must pass the law), says his members aren’t likely to push through such legislation at all this year.

“There are a lot of details to work through,” notes Johnson. He’s worried that a paid-vacation mandate might hurt already hard-hit small-business owners.

And by the way, the bill was first introduced five years ago. Who knows when — or if — it will ever pass?

Falsehood No. 3: De Blasio claims the Justice Department ordered him not to take action against NYPD Officer Daniel Pantaleo (the cop accused of using excessive force on Eric Garner while trying to arrest him in 2014) for the past five years because DOJ was conducting its own investigation.

The Washington Post’s Fact Checker gave him “Four Pinocchios” for that one. The NYPD, it said, was free to start proceedings against Pantaleo years ago and, in fact, did just that well before DOJ closed its own investigation this year.

The list of de Blasio fibs goes on and on. And while we’re glad he hasn’t actually accomplished much of what he says he has, it’s surely not right for him to lie about it.