1. divisjon

1. divisjon is the second-highest level of the Norwegian football league system. Since the 2015 season, it has been branded as OBOS-ligaen, after a six-year deal was agreed with the housing cooperative OBOS.

Formally, it was a semi-professional league.

History
Between 1963 and 1990, the second highest level in Norwegian football was named 2. divisjon. In 1991, due to rebranding of the top flight level in 1990, it was renamed to its initial name; 1. divisjon. 1. divisjon has been the name of this level ever since, except for periods when the league has had a sponsor-affiliated name. Between 2005 and 2013 the level was known as Adeccoligaen and from 2015 to 2020 the name is OBOS-ligaen.

Previous
In the 1997 season, 1. divisjon merged from two divisions consisting of 12 teams each, to only one with 14 teams. In the 2001 season, 1. divisjon expanded from 14 to 16 teams. Only two teams were relegated in the 2000 seson. In 2009, the number of teams in Eliteserien expanded from 14 to 16. Therefore, only one team was relegated to 1. divisjon, whilst three teams were promoted to Tippeligaen.

Current
Since 2012 four teams, finishing 3rd to 6th, has qualified for promotion play-offs. In the 2017 season the relegation format was changed. The previous format where four teams were relegated was replaced with a format with two relegation spots and one relegation play-off spot.

The league is contested by 16 teams. During the course of a season, each club plays the others twice, home and away, for a total of 30 games for each club, and a total of 240 games in a season. The season starts in April and lasts until early November. The top two teams will be promoted to Eliteserien, while the teams placed from third to sixth place will play a promotion-playoff against each other to earn the right to play a two-legged game against the 14th-placed team in Eliteserien to win promotion. The bottom two teams will be relegated to the 2. divisjon known as PostNord-ligaen, and the team in 14th place will play a two-legged playoff against the play-off winner among the two second-placed teams in 2. divisjon.

Current members
The following 16 clubs are competing in the OBOS-ligaen during the 2018 season, seven of which are located in Western Norway, six are from Eastern Norway, and one each are from Trøndelag, Southern Norway and north of the Arctic Circle: