1990–91 NSL Cup

The 1990–91 NSL Cup was the 15th edition of the NSL Cup, which was the main national association football knockout cup competition in Australia.

South Melbourne were the defending champions, having defeated Sydney Olympic to win their first title in the previous year's final, but they were eliminated in the semi-finals by eventual winners Melita Eagles.

Melita Eagles defeated Preston Makedonia 1–0 in the final to win their first NSL Cup title.

Teams
The NSL Cup was a knockout competition with 14 teams taking part all trying to reach the Final in April 1991. The competition consisted of the 14 teams from the National Soccer League.

First round
Melita Eagles and Preston Makedonia had a bye for the First round.