1990–91 Courage League National Division One
| 1990–91 Courage League National Division One | |
|---|---|
| Countries | England |
| Date | 22 September 1990 – 27 April 1991 |
| Champions | Bath (2nd title) |
| Runners-up | Wasps |
| Relegated | Moseley Liverpool St Helens |
| Matches played | 78 |
The 1990–91 Courage League National Division One was the fourth season of the first tier of the English league system, currently known as the Gallagher Premiership. Wasps were the defending champions and the league was expanded to thirteen teams, with new sides Northampton and Liverpool St Helens promoted from the 1989–90 Courage League National Division Two. Each team played each other once.
Bath finished the season the champions for the second time, beating the holders Wasps by just one point. The two bottom sides, Moseley and Liverpool St Helens, were relegated to the 1991–92 Courage League National Division Two.