| Competition: | Primera División de México |
| Season: | 2003−04 |
| Winners: | Pachuca (3rd title) |
| Continentalcup1: | Champions' Cup |
| Continentalcup1 Qualifiers: | Pachuca |
| Continentalcup2: | Copa Libertadores |
| Continentalcup2 Qualifiers: | América Santos Laguna |
| League Topscorer: | Luis Gabriel Rey (15 goals) |
| Prevseason: | Clausura 2003 |
| Nextseason: | Clausura 2004 |
Primera División de México (Mexican First Division) Apertura 2003 is a Mexican football tournament - one of two short tournaments that take up the entire year to determine the champion(s) of Mexican football. It began on Saturday 2 August 2003, and ran until 22 November, when the regular season ended. Irapuato was promoted to the Primera División de México to play this tournament, and Cuernavaca was to be relegated to the Primera División A. The Cuernavaca did not get to play in Primera A, though, as the team was disbanded by FMF. On 20 December, Pachuca defeated Tigres UANL and became champions for the third time.
Players sorted first by goals scored, then by last name. Only regular season goals listed.
| Rank | Player | Club | Goals | ||
|---|---|---|---|---|---|
| align=center rowspan=1 | 1 |  Luis Gabriel Rey | Atlante | align=center rowspan=1 | 15 |
| align=center rowspan=1 | 2 | José Cardozo | Toluca | align=center rowspan=1 | 13 |
| align=center rowspan=2 | 3 | Carlos María Morales | Atlas | align=center rowspan=2 | 12 |
| Reinaldo Navia | Morelia | ||||
| align=center rowspan=2 | 5 |  Alex Fernandes | Monterrey | align=center rowspan=2 | 11 |
 Emilio Mora | Veracruz | ||||
| align=center rowspan=3 | 6 | Jared Borgetti | Santos Laguna | align=center rowspan=3 | 10 |
| Eliomar Marcón | UAG | ||||
 Alfredo Moreno | Necaxa | ||||
| align=center rowspan=4 | 9 | Cuauhtémoc Blanco | América | align=center rowspan=4 | 9 |
| Walter Gaitán | UANL | ||||
| Luis Ignacio Quinteros | Puebla | ||||
| Andrés Silvera | UANL |
Source: MedioTiempo
Toluca won 6–4 on aggregate.----
Cruz Azul won 4–1 on aggregate.
2–2 on aggregate. UANL advanced for being the higher seeded team.----
Toluca won 4–2 on aggregate.----
Pachuca won 4–3 on aggregate.----
Atlante won 5–3 on aggregate.
UANL won 2–1 on aggregate.----
Pachuca won 2–1 on aggregate.
Pachuca won 3–2 on aggregate.