Gaga goes batty!

Gaga goes batty! Lady Gaga was no lady at Citi Field yesterday. The eccentric singer stripped down to her bra and bikini bottom and boorishly barraged fans and photographers with a double-barrel bird-flipping during a bizarre, profanity-laced meltdown. bwen

Gaga showed up during the fifth inning of the day game against the San Diego Padres and was furious that her front-row seats were so close to photographers covering the game.

Instead of sitting, she vanished into a lower-deck concourse -- only to reappear in the seventh inning in the empty luxury box owned by Met super-fan Jerry Seinfeld.

By the time fans and photographers spotted her, she had shed her coat to reveal bedazzled undies that looked like the get-up she wore in the video for her single "Telephone."

The beer-swilling diva -- who has professed her love for the Yankees -- proceeded to repeatedly salute the crowd with her middle finger.

When fans rose for the seventh-inning stretch, she did, too -- dancing and giving onlookers the double-bird salute.

She watched the rest of the game in just her undergarments without incident.

"She was psyched to go the game," a source close to Gaga told The Post. "But she felt it was unfair that she was seated right by the paparazzi. Having them take pictures of her all game would've been annoying to all the fans. That was going to ruin it for everyone."

A pal admitted the singer cursed out photographers.

"She went up to the box and said, 'F- - - you! F- - - you!' bwen to the photographers who were messing up the game for everyone else," the pal said.