| Competition: | Copa Mustang |
| Season: | 2003 |
| Winners: | Apertura: Once Caldas (2nd title) Finalización: Deportes Tolima (1st title) |
| Relegated: | Centauros Villavicencio |
| Continentalcup1: | Copa Libertadores |
| Continentalcup1 Qualifiers: | Once Caldas Deportes Tolima Deportivo Cali |
| Continentalcup2: | Copa Sudamericana |
| Continentalcup2 Qualifiers: | Junior Millonarios |
| League Topscorer: | Apertura: Arnulfo Valentierra (13 goals) |
| Matches: | 376 |
| Total Goals: | 897 |
| Prevseason: | 2002 |
| Nextseason: | 2004 |
The 2003 Categoría Primera A season was the 55th season of Colombia's top-flight football league. The season started on 2 February and concluded on 21 December 2003. Independiente Medellín were the defending champions, having won the 2002 Finalización tournament.
The Torneo Apertura (officially the 2003 Copa Mustang I for sponsorship reasons) was the first tournament of the season. The tournament began on February 2 and ended on June 8.
The second phase of the tournament consisted of two groups of four teams each. This was played by the best eight teams from the first phase of the tournament. The winners of each group qualified for the Finals.
| width=16% | Date | width=10% | City | width=30% | Home | width=7% | Score | width=30% | Away |
|---|---|---|---|---|---|---|---|---|---|
| June 5 | Barranquilla | Junior | 0–0 | Once Caldas | |||||
| June 8 | Manizales | Once Caldas | 1–0 | Junior | |||||
| Once Caldas won 1–0 on aggregate score | |||||||||
| Rank | Name | Club | Goals | ||
|---|---|---|---|---|---|
| align=center | 1 |  Arnulfo Valentierra | Once Caldas | 13 | |
| align=center | 2 | Julián Vásquez | América de Cali | 11 | |
| align=center | 3 | Leonardo Fabio Moreno | América de Cali | 10 | |
| align=center | 4 | Wilson Carpintero | Atlético Bucaramanga | 9 |
The Torneo Finalización (officially the 2003 Copa Mustang II for sponsorship reasons) was the second tournament of the season. The tournament began on July 13 and ended on December 21.
| width=16% | Date | width=10% | City | width=30% | Home | width=7% | Score | width=30% | Away |
|---|---|---|---|---|---|---|---|---|---|
| December 17 | Ibagué | Deportes Tolima | 2–0 | Deportivo Cali | |||||
| December 21 | Cali | Deportivo Cali | 3–1 | Deportes Tolima | |||||
| Tied 3–3 on aggregate score, Deportes Tolima won 4–2 on penalty kicks | |||||||||
| Rank | Name | Club | Goals | |
|---|---|---|---|---|
| align=center | 1 | Léider Preciado | Deportivo Cali | 17 |
| align=center | 2 |  Rogeiro Pereira | Deportes Tolima | 12 |
| 3 | Carlos Castillo | Deportivo Cali | 10 | |
| Julián Téllez | Millonarios | 10 |
An aggregate table including all games that a team played during the year was used to determine berths to both the Copa Libertadores and the Copa Sudamericana. The best-placed non-champion qualified for the 2004 Copa Libertadores along with both champions of the season, while the second and third best-placed non-champions qualified for the 2004 Copa Sudamericana.
| width=28 | width=185 | Team | width=28 | width=28 | width=28 | Relegation | ||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 108 | 222 | ||||||||
| 2 | 108 | 198 | ||||||||
| 3 | 108 | 181 | ||||||||
| 4 | 108 | 175 | ||||||||
| 5 | 108 | 175 | ||||||||
| 6 | 108 | 173 | ||||||||
| 7 | 108 | 172 | ||||||||
| 8 | 108 | 168 | ||||||||
| 9 | 108 | 168 | ||||||||
| 10 | 108 | 162 | ||||||||
| 11 | 108 | 162 | ||||||||
| 12 | 108 | 155 | ||||||||
| 13 | 108 | 152 | ||||||||
| 14 | 108 | 148 | ||||||||
| 15 | 108 | 146 | ||||||||
| 16 | 108 | 139 | ||||||||
| 17 | 108 | 138 | ||||||||
| 18 | 108 | 135 | ||||||||