P19 Allsvenskan is the highest level of men's association football for Swedish under-19 teams, and determines the under-19 (or junior) Swedish championships. The title has been officially contested since 1982 in different formats, IFK Göteborg being the most successful team with nine titles.
The junior championships for club teams (juniormästerskap för klubblag, also junior-SM or JSM) for boys have been played since 1982, but the competition had several unofficial precursors. A cup tournament, Allsvenska ungdomscupen, was played from 1945 to 1976, and was open to member clubs of the Swedish Professional Football Leagues. The title unofficial junior champions was awarded to the winners of the tournament, which was discontinued when the newspaper Expressen withdrew their sponsorship. For the years between 1949 and 1958, the winner of this cup also played a national final (Riksfinal) against the winners of the Norrland junior championships (Norrländska juniormästerskapen).
The Swedish Professional Football Leagues also arranged a league starting in 1971, Allsvenska ungdomsserien, only open to youth teams of Allsvenskan clubs. A champion was decided through a final match between group winners, and was open to all Swedish Professional Football Leagues members from 1977. This league was sometimes also called Allsvenska utvecklingsserien, and saw continued play in parallel to the in 1982 introduced official junior championships, initially played in a strict cup format.
In 1990, the youth league was rebranded as Juniorallsvenskan, and the play-off following the league replaced the separate cup tournament as the competition to decide the official junior champions. The championship is played in league format, currently named P19 Allsvenskan, until 2021 consisting of two regional groups, followed by a final between the two winning teams to determine the junior champions. From 2022, the league format has been changed to consist of a single group of 14 teams with no play-off.
From 1982 until 2008, the championships were played with an age limit of 18, but from 2009 on the age limit has been 19.