Malmö FF were the defending champions after winning the title in the previous season, and they defended the championship in the 30th and final round on 4 December 2021 and secured their 22nd Swedish championship title by playing a scoreless tie at home against Halmstads BK, resulting in Malmö FF winning the title on better goal difference than the runner-up (AIK).
The 2021 Allsvenskan season began on 10 April and ended on 4 December 2021 (not including play-off matches).
A total of sixteen teams are contesting the league, including fourteen sides from the previous season, and two promoted teams from the 2020 Superettan.
Falkenbergs FF and Helsingborgs IF (both relegated after two years in the top flight) were relegated at the end of the 2020 season after finishing at the bottom two places of the table, and were replaced by the 2020 Superettan champions Halmstads BK (promoted after a three-year absence) and runners-up Degerfors IF (promoted after a twenty-three-year absence).
Note: Flags indicate national team as has been defined under FIFA eligibility rules.