The actor and comedian, 45, has been losing weight for some time and last night he showed off an even slimmer physique while supporting his movie Birdman at the LA ceremony.
Fans were quick to share their thoughts on his weight loss, with many branding the Hollywood actor "unrecognizable" thanks to his hard work.
One tweeted: "If someone had told me this was Zach Galifianakis, I wouldn't have known."
Another said: "Wow! What a hottie! Zack Galifianakis. Looks so good!"
Zach and his Birdman co-stars won the 'Outstanding Performance by a Cast in a Motion Picture' prize at Sunday night's glitzy awards show.
The movie revolves around a faded Hollywood actor played by Michael Keaton. He's famous for a superhero role he played in the past and now he's trying to stage a Broadway adaptation of a Raymond Carver story.
It's been a huge success during this awards season, picking up Golden Globe Awards, SAG Awards, Critics' Choice Awards and a massive nine Oscar nominations.
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