| Competition: | 1. divisjon |
| Season: | 2020 |
| Dates: | 3 July – 13 December |
| Winners: | Tromsø |
| Promoted: | Tromsø Lillestrøm |
| Relegated: | Kongsvinger Øygarden |
| Matches: | 240 |
| Total Goals: | 781 |
| League Topscorer: | Henrik Udahl (19 goals) |
| Biggest Home Win: | |
| Biggest Away Win: | |
| Highest Scoring: | |
| Longest Wins: | 8 games Tromsø[1] |
| Longest Unbeaten: | 14 games Lillestrøm |
| Longest Winless: | 10 games HamKam |
| Longest Losses: | 6 games Kongsvinger |
| Prevseason: | 2019 |
| Nextseason: | 2021 |
The 2020 1. divisjon (referred to as OBOS-ligaen for sponsorship reasons) was a Norwegian second-tier football league season.
In the 2019 1. divisjon, Aalesund, Sandefjord and Start were promoted to the 2020 Eliteserien, while Notodden, Skeid and Tromsdalen were relegated to the 2020 2. divisjon.
Lillestrøm, Tromsø and Ranheim were relegated from the 2019 Eliteserien, while Stjørdals-Blink, Grorud and Åsane were promoted from the 2019 2. divisjon.
| Team | Location | Arena | Capacity | Manager |
|---|---|---|---|---|
| Åsane | Bergen | Myrdal gress | 2,180[2] |  Morten Røssland |
| Grorud | Oslo | Grorud Matchbane | 1,700[3] | Eirik Kjønø |
| HamKam | Hamar | Briskeby Arena | 7,800 | Kjetil Rekdal |
| Jerv | Grimstad | Levermyr Stadion | 3,300 | Arne Sandstø |
| KFUM Oslo | Oslo | KFUM Arena | 1,500 | Jørgen Isnes |
| Kongsvinger | Kongsvinger | Gjemselund Stadion | 5,824 | Espen Nystuen (interim) |
| Lillestrøm | Lillestrøm | Åråsen Stadion | 11,500 | Geir Bakke |
| Øygarden1 | Øygarden | Ågotnes Stadion | 1,200 | Mons Ivar Mjelde |
| Ranheim | Trondheim | Extra Arena | 3,000 | Svein Maalen |
| Raufoss | Raufoss | Nammo Stadion | 1,800 | Christian Johnsen |
| Sandnes Ulf | Sandnes | Øster Hus Arena | 6,046 | Steffen Landro |
| Sogndal | Sogndal | Fosshaugane Campus | 5,622 | Eirik Bakke |
| Stjørdals-Blink | Stjørdalshalsen | M.U.S Stadion | 2,000[4] | Roar Vikvang |
| Strømmen | Strømmen | Strømmen Stadion | 2,000 | Ole Martin Nesselquist |
| Tromsø | Tromsø | Alfheim Stadion | 6,687 | Gaute Helstrup |
| Ull/Kisa | Jessheim | Jessheim Stadion | 4,500 | Trond Fredriksen |
| Team | Outgoing manager | Manner of departure | Date of vacancy | Table | Incoming manager | Date of appointment | Table |
|---|---|---|---|---|---|---|---|
| Sandnes Ulf | Bengt Sæternes | Contract expired | 31 December 2019 | Pre-season | Steffen Landro | 13 November 2019[6] | Pre-season |
| Øygarden | Steffen Landro | Signed by Sandnes Ulf | 13 November 2019 |  Bryant Lazaro | 17 February 2020[7] | ||
| Kongsvinger | Vítor Gazimba | Mutual consent | 11 December 2019[8] |  Mika Lehkosuo | 18 December 2019[9] | ||
| Lillestrøm | Tom Nordlie | Contract expired | 11 December 2019[10] | Geir Bakke | 1 January 2020[11] | ||
| Tromsø | Simo Valakari | Mutual consent | 20 April 2020[12] | Gaute Helstrup | 20 May 2020[13] | ||
| HamKam | Gaute Helstrup | Signed by Tromsø | 19 May 2020[14] | Espen Olsen | 21 May 2020[15] | ||
| HamKam | Espen Olsen | Structural changes | 7 August 2020 | 16th | Geir Frigård (interim) | 7 August 2020[16] | 16th |
| HamKam | Geir Frigård (interim) | End of caretaker spell | 15 August 2020 | 16th | Kjetil Rekdal | 15 August 2020[17] | 16th |
| Øygarden | Bryant Lazaro | Mutual consent | 18 September 2020[18] | 14th | Mons Ivar Mjelde | 18 September 2020[19] | 14th |
| Kongsvinger | Mika Lehkosuo | Structural changes | 30 September 2020[20] | 16th | Espen Nystuen (interim) | 30 September 2020[21] | 16th |
See main article: 2020 Eliteserien promotion/relegation play-offs. The 3rd to 6th placed teams took part in the promotion play-offs; these were single leg knockout matches. In the first round, the 5th placed team played at home against the 6th placed team. The winner of the first round then met the 4th placed team on away ground in the second round. The winner of the second round then met the 3rd placed team on away ground. The winner of the third round advanced to play the 14th placed team in Eliteserien on neutral ground 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 2. divisjon play-offs to decide who would play in the 2021 1. divisjon.
Stjørdals-Blink won 6–1 on aggregate.