Lady Gaga is wearing just her undies to promote her new campaign "A Body Revolution."

The "Born This Way" singer posted the above photos on her Little Monsters website and revealed that she's been struggling with "bulimia and anorexia since I was 15."

Gaga said she started the campaign "to inspire bravery and breed some motherf**king compassion."

As Madonna would say ... "Strike a pose (in your yellow underwear), there's nothing to it..."