| Competition: | Irish League |
| Season: | 1939–40 |
| Winners: | Belfast Celtic 13th Irish title |
| Matches: | 182 |
| Total Goals: | 869 |
| Prevseason: | 1938–39 |
| Nextseason: | 1947–48 (official) 1940–41 (unofficial) |
The 1939–40 Irish League was the 46th edition of the Irish League, the highest level of league competition in Northern Irish football. The league comprised 14 teams, and Belfast Celtic won the championship.