A transit union leader is taking on Gov. Kathy Hochul, calling her a “snake” in a holiday-themed advertisement.

“Centuries ago, St. Patrick famously drove Ireland’s snakes into the sea, purging the Emerald Island of these reptiles forever, but he missed one — now we wish St. Patrick would come back and rid New York of Governor Kathy Hochul, before she drags the whole Democratic Party down with her by attacking working families, healthcare, retiree benefits and wages,” John Samuelsen, international president of the Transport Workers Union, said in the advertisement.

The 30-second TWU advertisement, obtained exclusively by NY1, is set to play statewide on television and social media through the St. Patrick’s Day weekend.

“We have a governor in New York state, Kathy Hochul, who’s declaring herself to be Irish and particularly an Irish Catholic. Simultaneously, betraying her Irish roots by attacking blue collar commuter rail workers, and also declaring herself to be the face of the Democratic Party,” the union boss said.

Samuelsen, an Irish-American labor leader whose mother is from Derry, Ireland, is attacking Hochul, another Irish-American New Yorker whose grandparents hail from Ireland’s County Kerry.

“Kathy Hochul is demanding concessions on pensions, on healthcare, on wages on seniority, everything the trade union movement holds dear. Everything that the Democratic Party should stand for, everything that Hochul has come out against,” he said.

Samuelsen represents about 150,000 workers in the subways, railroads, airlines and other service industries.

In New York, he’s in the middle of contract negotiations with the MTA on behalf of Metro-North train mechanics and cleaners.

Fighting for higher wages and better healthcare sought by the 600 union members affected, part of the MTA’s 70,000 member workforce.

But Samuelsen argues Hochul is choosing sides.

“When workers see Democrats acting like Republicans, they actually vote for Republicans. They don’t get fooled,” he said. “The Democrats are supposed to stand up for working people. Governor Hochul is not standing up for working people.”

“Governor Hochul has been a staunch supporter of labor for her entire career, marching on picket lines, speaking at rallies and standing with working people,” Avi Small, spokesman for the governor, told NY1 in a statement.

Samuelsen clearly isn’t a Hochul fan. He endorsed Attorney General Letitia James for a gubernatorial run — before she dropped out.

And now, the TWU is playing offense over subway crime that’s directly affecting members — taking out a critical advertisement of MTA CEO and Chairman Janno Lieber and Manhattan District Attorney Alvin Bragg in the New York Post earlier this week.

“They put an ad in the paper. I was on Page 9 in The Post, better than being on Page Six!” Lieber told reporters on Tuesday, responding to the advertisement.

“I thought the outfit they put on me was slenderizing,” he continued. “My view is the NYPD is doing a hell of a job in the subway system. The governor [has] brought additional forces. The NYPD has the MTA’s full confidence.”

Union leaders are criticizing Hochul’s plan that inserts National Guard into the subway system. They argue that while they welcome additional law enforcement presence, they “do not go far enough.”

“They can’t solve that problem! So that’s a social services problem. That’s an investment into the fabric of the city in New York, and social services,” said Samuelsen.

Samuelsen told NY1 that the Saint Patrick’s Day advertisement buy will cost six figures.

The union plans to reveal additional critical ads of the governor in the coming days.