Sir Rod Stewart didn’t hold back on the red carpet while greeting King Charles and Queen Camilla after their recent U.S. trip to see President Donald Trump!

At Monday’s 50th anniversary celebration for The King’s Trust at London’s Royal Albert Hall, Rod congratulated the King on the royal couple’s recent 4-day U.S. trip … before twisting the knife, adding, “May I say, well done in the Americas. You were superb, absolutely superb … put that little ratbag in his place!”

Charles appeared to laugh it off while discussing the trip … even referencing a speech where he poked fun at America’s colonial history with a cheeky French joke.

But Rod wasn’t done — immediately cracking how Trump would’ve received the joke … “Exactly, that’s it, it went right over his head!”

The rocker looked thrilled with himself too … doing everything to contain his giggles, before sarcastically adding to Camilla, “I was just congratulating your husband on his wonderful performance in the Americas — so great, so brave, so proud.”