President Biden is being ridiculed for his latest blunder, appearing to call his predecessor, Donald Trump, the “sitting president.”

The gaffe-prone commander in chief’s blunder came during a speech in South Carolina on Saturday as he repeatedly called former President Trump a “loser.”

“You’re the reason I am president,” Biden, 81, told the crowd of Democratic leaders as he touted his record of “promises made and promises kept.”

“You’re the reason Donald Trump is a loser,” he said of his likely key challenger in the 2024 election.

But online commentators soon said Biden was the real loser as he slipped up while discussing how “American consumers are facing real confidence in the economy we’re building.

“Let me tell you who else is noticing that: Donald Trump,” Biden said before he stumbled on his words.

“Did you see what he recently said about … he wants to, he wants to see the economy crash this year? A sitting president,” he said without correcting himself.

“As they say in my faith, bless me father for, I mean, come on, man,” Biden continued.

His comment about the “sitting president” was met with widespread ridicule.

“OMG – Biden really called Trump the sitting president. The conspiracy theorists are going to have a field day with this one,” one user said on X.

“Did this Dummy just call Donald Trump the sitting President?” another wrote, adding laughing emojis.

A third user added: “Mash-potato-brain Joe Biden calls Trump the sitting president. Senile POS.”

Trump backers reveled in Biden’s slip-up, which appeared to corroborate the Republican frontrunner’s widely debunked claims to have won the 2020 presidential election amid alleged voter fraud.

“Isn’t he the sitting president?” wrote one user, who added an emoji that indicates suspicion.

“Biden accidentally told the truth … DJT is the sitting president,” a self-described “MAGA patriot” wrote.

It is just the latest slip-up for Biden, who is already the oldest-ever president and would be 86 at the end of his second term if he won reelection.

A recent New York Times poll found 71% of swing-state voters say Biden is “too old to be an effective president,” while just 39% said so of Trump, 77. Biden’s defenders say he’s simply prone to gaffes that are aggravated by a lifelong stutter.