| Competition: | 2. divisjon |
| Season: | 1981 |
| Winners: | Mjøndalen Sogndal |
| Promoted: | Mjøndalen Sogndal Molde |
| Relegated: | Ørn Bærum Skeid Tromsø Nessegutten Bergsøy |
| Prevseason: | 1980 |
| Nextseason: | 1982 |
The 1981 2. divisjon was a Norwegian second-tier football league season.
The league was contested by 24 teams, divided into two groups: A and B.[1] Both groups consisted of 12 teams. The winners of groups A and B were promoted to the 1982 1. division. The second-placed teams in groups A and B met the 10th-best finisher in 1. divisjon in a qualification round where the winner was promoted to 1. divisjon. The bottom three teams in both groups were relegated to the 3. division.
Mjøndalen won group A with 31 points. Sogndal won Group B with 31 points. Both teams were promoted to the 1982 1. Division. The second-placed teams, Pors and Molde, met Brann in the promotion play-offs. Molde won the qualification round on goal difference and won promotion.
Molde won the qualification round and was promoted to the 1. divisjon.