It’s a real SOB story.

The Kremlin fired back Thursday at President Biden after the commander-in-chief called his Russian counterpart, Vladimir Putin, a “crazy SOB” during a California fundraiser – with Moscow likening Biden to a pathetic “Hollywood cowboy.”

“The use of such language against the head of another state by the president of the United States is unlikely to infringe on our president, President Putin. But it debases those who use such vocabulary.” spokesman Dmitry Peskov said.

Biden, 81, made the crack about the former KGB spook during a San Francisco event Wednesday night, at which he called climate change “the last existential threat” to humanity.

“We have a crazy SOB like that guy Putin, and others, and we always have to worry about nuclear conflict, but the existential threat to humanity is climate,” the president added.

The “SOB” comment was “probably some kind of attempt to look like a Hollywood cowboy. But honestly, I don’t think it’s possible,” Peskov scoffed.

“Has Mr. Putin ever used one crude word to address you? This has never happened. Therefore, I think that such vocabulary debases America itself,” he added.

The dig came as relations between Russia and the West continue to sour following the death of Putin’s main political opponent, Alexei Navalny, at a remote prison colony last week.

Biden has said that he believes Navalny’s death was “a consequence of something that Putin and his thugs did.”

The Kremlin has criticized the United States’ reaction to the outspoken Putin critic’s passing as rushed and unjustified.

Dmitry Medvedev, a Putin ally who was president of Russia from 2008 to 2012, said this week that the real threat to world security was “useless old geezers, like Biden himself.”

The US president is “senile” and “ready to start a war with Russia,” Medvedev insisted.

With Post wires