The 2025 Norwegian First Division (referred to as OBOS-ligaen for sponsorship reasons) is a Norwegian second-tier football league season. The season started on 31 March 2025 and is scheduled to end on 8 November 2025, not including play-off matches.
The following teams have changed division since the 2024 season:
Promoted from Second Division
Relegated from Eliteserien
Promoted to Eliteserien
Relegated to Second Division
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The teams from third to sixth place will take part in the promotion play-offs; these are single leg knockout matches. In the first round, the fifth-placed team will play at home against the sixth-placed team. The winner of the first round will meet the fourth-placed team on away ground in the second round. The winner of the second round will meet the third-placed team on away ground. The winner of the third round will face Bryne, the 14th-placed team in the Eliteserien over two legs in the Eliteserien play-offs for a spot in the top-flight next season.
The 14th-placed team took part in a two-legged play-off against the winners of the Second Division play-offs, to decide who would play in the First Division next season.