| Competition: | 2. divisjon |
| Season: | 1978 |
| Winners: | Mjøndalen (Group A) Rosenborg (Group B) Tromsø (Group C) |
| Promoted: | Mjøndalen (Group A) Rosenborg (Group B) HamKam (Group B) |
| Relegated: | Strømsgodset (Group A) Strømmen (Group B) Kongsvinger (Group B) Harstad (Group C) Stålkameratene (Group C) Grand Bodø (Group C) Alta (Group C) Mosjøen (Group C) Lyngen (Group C) Brønnøysund (Group C) |
| Prevseason: | 1977 |
| Nextseason: | 1979 |
The 1978 2. divisjon was a Norwegian second-tier football league season.
The league was contested by 30 teams, divided into a total of three groups; A and B (non-Northern Norwegian teams) and Group C, a district group which contained teams from Northern Norway.[1] The winners of group A and B were promoted to the 1979 1. divisjon. The second placed teams in group A and B met the winner of group C in a qualification round where the winner was promoted to 1. divisjon. The bottom team in group A and B and the seven lowest ranked teams in group C were relegated to the 3. divisjon. The second last teams in group A and B met in a two-legged qualification round to avoid relegation.
Mjøndalen won group A with 29 points. Rosenborg won group B with 27 points. Both teams promoted to the 1979 1. divisjon. Tromsø won group C and qualified for and the promotion play-offs but was not promoted.
Os won 3–1 on aggregate. Strømmen was relegated to 3. divisjon.