The 'Born This Way' singer was joined by artists including Justin Bieber, LMFAO, Drake, Cee Lo Green, Pitbull and Florence + the Machine for Dick Clark's New Year's Rockin' Eve live in Times Square.
GaGa performed a medley of 'Heavy Metal Lover', 'Marry the Night' and 'Born This Way' - as seen in the video above - in a costume that has been described by critics as "Jabba the Hut-esque".
She later changed into a black sequin bodysuit and Catwoman mask, while sporting a large globe structure around her head. GaGa also helped New York City mayor Michael Bloomberg drop the New Year's Eve ball, before kissing him at the stroke of midnight.
The 25-year-old tweeted after the show: "I cant even quite describe what tonight felt like. Sort of poetic madness. A dream come true. Moments recalling a leather taking the subway.
"My new years resolution: Never be afraid to be kicked in the teeth. Let the blood and the bruises define your legacy."
Justin Bieber took to the piano to cover The Beatles' 'Let It Be' alongside Carlos Santana, and later declared that he was "honoured" to have performed with the legendary guitar player.
LMFAO, Drake, Cee Lo Green, Pitbull and Florence + the Machine also played the annual gig across the evening.
Dick Clark has hosted the New Year's Eve spectacle since the 1970s and was again aided by Ryan Seacrest for what was the 40th anniversary of the show.