The singer is officially 21 on Sunday, and his pal Hailey Baldwin posted this snap with him looking pensive on Saturday.
And he didn't put a shirt on with his former rumored romantic interest Yovanna Ventura either. Ventura shared this intimate moment.
More photos of Bieber were put together by the Shots photo-sharing platform for Bieber's big day so that fans could relieve some his best moments.
Bieber also got in some social sharing as he tweeted about the milestone he reached after #HappyBirthdayJustinBieber trended. He said, "Grateful to be alive!! Love u!! 21" and "I love everybody! #21."
To see more of Justin Bieber shirtless, check out his Calvin Klein ads in the video below.