Billionaire Democrat activist Tom Steyer is using his fortune to combat what he thinks is the greatest threat to America.

No, not ISIS or Ebola. To help favored congressional candidates, he’s running an ad that highlights pollution from an oil refinery owned by Charles and David Koch — whose political donations largely favor the party Steyer opposes.

And never mind the fact that Steyer had no qualms about fossil fuel back when his hedge fund was making millions in the industry.

With this effort, Steyer joins a long list of green activists who use fossil-fuel profits to bash the industry that fed them.

What makes the hypocrisy truly outrageous is that these activists promote policies that will prevent average Americans from sharing in the benefits of the energy boom.

Consider George Soros, the world’s richest hedge-fund manager. He supports groups such as Alliance for Climate Change, the Natural Resources Defense Council and the Union of Concerned Scientists — which all oppose the job-creating innovation known as hydraulic fracturing, or “fracking.”

Yet Soros himself recently bought a giant stake in CONSOL Energy, a company actively involved in fracking. Hmm . . .

Perhaps what really bothers the powers in the green movement is that — unlike themselves — the energy sector gives American consumers something they actually want.

Even Al Gore took a fossil-fuel payday. He sold his TV channel to Al Jazeera Media Network, a foreign news outfit heavily backed by oil money.

Gore defended his decision, saying that the channel was struggling and that Al Jazeera would “give thorough coverage to the climate-change issue.”

Weeks later, Gore released a book in which he blames the poor state of the climate-change debate on the fact that “virtually every news and political-commentary program on television is sponsored in part by oil, coal and gas companies.”

As for Steyer, he left his $20 billion hedge fund back in 2012, promising to pull his personal holdings from “ecologically unsound” investments.

Did he back up his loud, proud, moral stand by immediately dumping his energy assets, no matter the personal loss? Hah: Steyer waited until market conditions were optimal for reaping some final profits from the energy sector.

Steyer has described his conversion to climate activism as a “personal version of a ‘Paul on the Road to Damascus’ moment.”

A more apt analogy might be to Michael Corleone from “The Godfather”: Just when Steyer thought he was out, energy profits pulled him back in.

He needed these profits so he could pump $100 million to Democratic politicians who prevent others from making profits and creating jobs in the energy sector.

More than a few environmental groups have dipped their hand into the fossil-fuel till, far from view of their donors and the public.

Take the Nature Conservancy — the largest US environmental activist outfit, buying over 20 million acres in the name of conservation. Funny: The group makes millions off oil and natural gas.

In one notable scandal, the Nature Conservancy raised millions from well-intentioned donors to buy land to help protect a threatened species, the Attwater’s prairie chicken, from extinction.

But after the purchase, it approved oil drilling there. The endangered birds are no longer on the land, but the group continues to grow rich off of oil profits.

After a two-year Senate investigation and exposure by the Los Angeles Times, the Nature Conservancy promised to cease new oil drilling on its lands.

But it apparently decided it likes cash more than endangered species, and expanded fossil-fuel extraction on the land despite its promise.

Environmental groups are not above taking bribes, either. From 2007 to 2010, the Sierra Club accepted $25 million in secret payments from a natural-gas company for Sierra’s anti-coal campaign.

Perhaps what really bothers the powers in the green movement is that — unlike themselves — the energy sector gives American consumers something they actually want.

The oil and natural-gas industry is responsible for 9.8 million American jobs. Another 1.4 million could be added by 2030, if the federal government lifts its blockade on access to natural resources.

It’s difficult to take the environmentalist leaders seriously. Over and over, the movement attacks a sector that’s a vital part of the American economy.

So the next time a green activist demands America pay more for energy, opt out of air conditioning or divest from fossil-fuel stocks, the American voters should simply say, “You first.”

Michael James Barton is the director for energy at ARTIS Research. He previously served as the deputy director of Middle East policy at the Pentagon.