| 1990 O'Byrne Cup | |
| Province: | Leinster |
| Year: | 1990 |
| Date: | 7 April — 23 May |
| Num Teams: | 11 |
| Trophy: | O'Byrne Cup |
| Winners: | Louth |
| Manager: | Frank Lynch |
| Captain: | Gerry Farrell |
| Runnersup: | Kildare |
| Runnerupmanager: | Pat Fitzgerald |
| Ordinal: | 3 |
| Previous: | 1989 |
| Next: | 1991 |
The 1990 O'Byrne Cup was a Gaelic football competition contested by the county teams of Leinster GAA.
The tournament format was straight knockout, with 11 participating teams. Dublin did not enter the competition. First-round byes were awarded to Laois, Louth, Meath, Longford and Kildare.
Louth won the competition after defeating Kildare in the final, held at the Drogheda Gaelic Grounds.