Crappy birthday, Rudy.

Former Mayor Rudy Giuliani celebrated his 74th birthday at Yankee Stadium on Monday — where the crowd gave him a big Bronx jeer for his big day.

The boos went up as the Yankees wished Giuliani a happy birthday over the loudspeaker.

The heckles weren’t as loud as those for the Houston Astros, however.

The man once known as “America’s Mayor” recently joined President Trump’s legal team amid the federal probe into Russian election interference and has been a regular presence on TV news shows supporting the commander in chief.

But this isn’t the first time he’s faced backlash from other Bombers fans — he was reportedly booed by the crowd at a game back in 2007.