1990–91 in Argentine football

The 1990–91 season saw the introduction of the Apertura and Clausura system in Argentina. Newell's Old Boys won the Apertura 1990 and Boca Juniors won the Clausura 1991. The two teams faced each other in a playoff to decide the overall champions, which was won by Newell's. There was a great deal of controversy over this as Boca Juniors had won the Clausura without losing a game, but losing the playoff had cost them their first official championship since 1981. In subsequent seasons the winners of both the Apertura and Clausura have been officially recognised as champions.