The 79-year-old, who has been married three times, acknowledged mid-speech that his remark might be deemed politically incorrect.
“I’m not allowed to say it, because usually it’s the end of your political career if you do,” Trump said while discussing his peace efforts in the Middle East. “But she’s a beautiful young woman I’ll take my chances.”
Turning toward Meloni, 48, Trump added, “You don’t mind being called beautiful, right? Because you are.”
Meloni’s immediate reaction was not visible, as Trump’s back was turned to the cameras.
Trump, who has previously praised Meloni’s conservative leadership, went on to describe her as “incredible,” adding that “they really respect her in Italy she’s a very successful politician.”
The exchange quickly drew attention online, with many noting that Trump’s remarks overshadowed parts of his address on Gaza’s peace efforts.
Meloni was the only woman among around 30 leaders gathered on the stage behind Trump for the summit, where they signed a declaration pledging to help push through peace for Gaza.
Trump has previously been criticised for sexist remarks.
In September, a US appeals court upheld a jury's $83.3-million penalty against Trump for defaming author E. Jean Carroll, whom he was found to have sexually assaulted.