The 1. divisjon 1991 was the 29th season of the second highest Norwegian football league and the first under the name 1. divisjon . It began on April 28, 1991 and ended on October 6, 1991.
The 24 teams were divided into two groups of 12 teams each. They played against each other twice on 22 match days, divided into a first round and a second half. The two group winners were promoted directly to the 1st division. The two runners determined with the 10th of Tippeligaen another starting position for the Tippeligaen. The last three clubs were relegated to the 2nd divisjon.