The 32-year-old terminated his contract with Arsenal which still had 18 months to run on Tuesday and he arrives at the Camp Nou as a free agent.
Aubameyang had already been training with Barcelona this week once it became clear that his spell at the Gunners was coming to an end.
The Gabon international joined Arsenal from Borussia Dortmund in January 2018 and he scored 92 goals in 162 appearances for the club.
Aubameyang led Arsenal to FA Cup glory in the 2019/2020 season but was stripped of the captaincy in December after a disciplinary breach.
Aubameyang has signed a three-and-half year contract with Barcelona.
"FC Barcelona and Pierre-Emerick Aubameyang have reached an agreement for the player to join the club after the striker terminated his contract with Arsenal FC," a statement on the Blaugrana's official website reads.
"The player will sign a contract until 30 June 2025 with an option to agree departure on 30 June 2023 and his buy-out clause will be set at 100 million euros.
"Shortly the club will provide details of Pierre-Emerick Aubameyang's presentation as a first-team player."
Aubameyang’s arrival means Barcelona have brought in four players in the January transfer window including Daniel Alves, Ferran Torres and Adama Traore.
