| Club: | Osasuna |
| Season: | 2003–04 |
| Chrtitle: | President |
| Chairman: | Patxi Izco |
| Mgrtitle: | Head coach |
| Manager: | Javier Aguirre |
| Stadium: | El Sadar |
| League: | La Liga |
| League Result: | 13th |
| Cup1: | Copa del Rey |
| Cup1 Result: | Round of 16 |
| League Topscorer: | John Aloisi (6) |
| Season Topscorer: | John Aloisi (8) |
| Largest Win: | Real Madrid 0–3 Osasuna |
| Largest Loss: | Osasuna 0–2 Valencia Deportivo La Coruña 2–0 Osasuna Osasuna 1–3 Espanyol |
| Prevseason: | 2002–03 |
| Nextseason: | 2004–05 |
The 2003–04 season was the 83rd season in the existence of CA Osasuna and the club's fourth consecutive season in the top flight of Spanish football. In addition to the domestic league, Osasuna participated in this season's edition of the Copa del Rey.[1] The season covered the period from 1 July 2003 to 30 June 2004.
See main article: 2003–04 La Liga.
See main article: 2003–04 Copa del Rey.