| Competition: | Primera B Nacional |
| Season: | 1990–91 |
| Winners: | Quilmes (1st divisional title) |
| League Topscorer: | Roberto Oste (24 goals) |
| Prevseason: | 1989–90 |
| Nextseason: | 1991–92 |
The 1990–91 Argentine Primera B Nacional was the fifth season of second division professional of football in Argentina. A total of 22 teams competed; the champion and runner-up were promoted to Argentine Primera División.
| Club | City | Stadium | |
|---|---|---|---|
| Almirante Brown | Isidro Casanova | Fragata Presidente Sarmiento | |
| Atlanta | Villa Crespo | León Kolbovski | |
| Atlético de Rafaela | Rafaela | Nuevo Monumental | |
| Atlético Tucumán | San Miguel de Tucumán | Monumental Presidente Jose Fierro | |
| Banfield | Banfield | Florencio Solá | |
| Belgrano | Córdoba | El Gigante de Alberdi | |
| Central Córdoba | Santiago del Estero | Alfredo Terrara | |
| Cipolletti | Cipolletti | La Visera de Cemento | |
| Colón | Santa Fe | Brigadier General Estanislao López | |
| Florencio Varela | Norberto "Tito" Tomaghello | ||
| Deportivo Laferrere | Gregorio de Laferrere | José Luis Sánchez | |
| Deportivo Maipú | Maipú | Higinio Sperdutti | |
| Deportivo Morón | Morón | Francisco Urbano | |
| Douglas Haig | Pergamino | Miguel Morales | |
| Instituto | Córdoba | Presidente Perón | |
| Quilmes | Quilmes | Centenario | |
| Racing | Córdoba | Miguel Sancho | |
| San Martín | San Miguel de Tucumán | La Ciudadela | |
| Sportivo Italiano | Ciudad Evita | Republica de Italia | |
| Talleres | Remedios de Escalada | Talleres de Remedios de Escalada | |
| Tigre | Victoria | José Dellagiovanna | |
| Villa Dálmine | Campana | El Coliseo |
Quilmes was declared champion and was automatically promoted to Primera División, and the teams placed 2nd to 10th qualified for the Second Promotion Playoff.
The Second Promotion Playoff or Torneo Reducido was played by the teams placed 2nd to 11th in the overall standings: Atlético Tucumán (2nd), who entered in the Semifinals, Belgrano (3rd), who entered in the Second Round, and in the first round entered San Martín (T) (5th), Banfield (6th), Almirante Brown (7th), Instituto (8th), Douglas Haig (9th), Deportivo Morón (10th) and Atlético de Rafaela (11th), (Cipolletti (4th) did not qualify because it was relegated). In the first round also participated the champion of Primera B Metropolitana: Central Córdoba (R), and Nueva Chicago and San Martín (SJ), both winners of Zonales Noroeste y Sureste from Torneo del Interior. The winner was promoted to Primera División.
1: Qualified because of sport advantage.
----
| width=28 | width=185 | Team | width=50 | width=50 | width=50 | width=50 | width=50 | width=50 | Situation | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Belgrano | 50 | 47 | 52 | 149 | 126 | Indirect | ||||||||||
| 2 | San Martín (T) | — | 48 | 48 | 96 | 84 | Indirect | ||||||||||
| 3 | Quilmes | 37 | 53 | 54 | 144 | 126 | Direct | ||||||||||
| 4 | Atlético Tucumán | 45 | 43 | 52 | 140 | 126 | Indirect | ||||||||||
| 5 | Banfield | 44 | 46 | 47 | 137 | 126 | Direct | ||||||||||
| 6 | Almirante Brown | 51 | 39 | 46 | 136 | 126 | Direct | ||||||||||
| 7 | Atlético de Rafaela | — | 47 | 42 | 89 | 84 | Indirect | ||||||||||
| 8 | Instituto | — | — | 44 | 44 | 42 | Indirect | ||||||||||
| 9 | Colón | 50 | 45 | 36 | 131 | 126 | Direct | ||||||||||
| 10 | Deportivo Morón | — | — | 43 | 43 | 42 | Direct | ||||||||||
| 11 | Douglas Haig | 32 | 51 | 44 | 127 | 126 | Indirect | ||||||||||
| 12 | Sportivo Italiano | 46 | 46 | 34 | 126 | 126 | Direct | ||||||||||
| 13 | Villa Dálmine | — | 44 | 39 | 83 | 84 | Direct | ||||||||||
| 14 | Talleres (RE) | 48 | 35 | 41 | 124 | 126 | Direct | ||||||||||
| 15 | Defensa y Justicia | 49 | 35 | 38 | 122 | 126 | Direct | ||||||||||
| 16 | Racing (C) | — | — | 40 | 40 | 42 | Indirect | ||||||||||
| 17 | Deportivo Laferrere | — | — | 39 | 39 | 42 | Direct | ||||||||||
| 18 | Deportivo Maipú | 43 | 35 | 38 | 116 | 126 | Relegation Playoff Matches | Indirect | |||||||||
| 19 | Central Córdoba (SdE) | 43 | 37 | 33 | 113 | 126 | Additional Playoff | Indirect | |||||||||
| 20 | Tigre | 30 | 41 | 42 | 113 | 126 | Direct | ||||||||||
| 21 | Cipolletti | 28 | 33 | 48 | 109 | 126 | Liga Deportiva Confluencia | Indirect | |||||||||
| 22 | Atlanta | — | — | 16 | 16 | 42 | Primera B Metropolitana | Direct |
Note: Clubs with indirect affiliation with AFA are relegated to their respective league of his province according to the Argentine football league system, while clubs directly affiliated face relegation to Primera B Metropolitana. Clubs with direct affiliation are all from Greater Buenos Aires, with the exception of Newell's, Rosario Central, Central Córdoba and Argentino de Rosario, all from Rosario, and Unión and Colón from Santa Fe.
Since Central Córdoba (SdE) and Tigre finished with the same relegation co-efficient at the dividing line, a one-match playoff was held to determine who was relegated. Tigre lost so their got relegated to Primera B Metropolitana, while Central Cordoba (SdE) remained in Primera B Nacional.
| Additional Playoff | |||||
|---|---|---|---|---|---|
| width=30% | Home | width=15% | Result | width=30% | Away |
| Central Córdoba (SdE) | 3 - 0 | Tigre |
Each tie was played on a home-and-away two-legged basis, but if the first match was won by the team of Primera B Nacional (who also played the first leg at home), there was no need to play the second. If instead, the team from the Regional leagues wins the first leg, the second leg must be played, leg that, if its won by the team of Primera B Nacional, a third leg must be played, if the third leg finishes in a tie, the team from Primera B Nacional remains on it.This season Deportivo Maipú had to defend their spot in Primera B Nacional against Godoy Cruz from the Liga Mendocina de fútbol.
| Relegation Playoff | |||||
|---|---|---|---|---|---|
| width=30% | Home | width=15% | Result | width=30% | Away |
| Deportivo Maipú | 2 - 1 | Godoy Cruz |