1981 NSL Cup
The 1981 NSL Cup was the fifth edition of the NSL Cup, which was the main national association football knockout cup competition in Australia.
Marconi Fairfield were the defending champions, having defeated Heidelberg United to win their first title in the previous year's final, but they were eliminated in the semi-finals by Brisbane Lions.
Brisbane Lions defeated West [Adelaide SC|West Adelaide] 3–1 in the final to win their first NSL Cup title.
Teams
The NSL Cup was a knockout competition with 36 teams taking part all trying to reach the Final in September 1981. The competition consisted of the 16 teams from the National Soccer League plus 20 teams from their respective top division state leagues.| Round | Main date | Number of fixtures | Clubs remaining |
| First round | Sunday 22 March 1981 | 16 | 36 → 20 |
| Second round | Wednesday 6 May 1981 | 10 | 20 → 10 |
| Third round | Tuesday 16 June 1981 | 2 | 10 → 8 |
| Quarter-finals | Wednesday 17 June 1981 | 4 | 8 → 4 |
| Semi-finals | Wednesday 5 August 1981 | 2 | 4 → 2 |
| Final | Sunday 20 September 1981 | 1 | 2 → 1 |