| Competition: | Serie B |
| Season: | 1990–91 |
| Winners: | Foggia 1st title |
| Promoted: | Verona Cremonese Ascoli |
| Relegated: | Salernitana Reggina Triestina Barletta |
| League Topscorer: | Francesco Baiano Abel Balbo Walter Casagrande (22 goals each) |
| Matches: | 380 |
| Total Goals: | 745 |
| Prevseason: | 1989–90 |
| Nextseason: | 1991–92 |
The Serie B 1990–91 was the fifty-ninth tournament of this competition played in Italy since its creation.
Modena, Lucchese, Taranto and Salernitana had been promoted from Serie C, while Udinese, Verona, Cremonese and Ascoli had been relegated from Serie A.
Salernitana relegated to Serie C1.