2004 Estoril Open – Men's singles

Nikolay Davydenko was the defending champion but lost in the first round to Radek Štěpánek.

Juan Ignacio Chela won in the final 6–7(2–7), 6–3, 6–3 against Marat Safin.

Seeds

 * 1) 🇩🇪 Rainer Schüttler (first round)
 * 2)  Nicolás Massú (first round)
 * 3) 🇦🇷 Agustín Calleri (first round)
 * 4) 🇪🇸 Tommy Robredo (quarterfinals)
 * 5) 🇦🇷 Juan Ignacio Chela (champion)
 * 6) 🇧🇾 Max Mirnyi (second round)
 * 7) 🇦🇷 Gastón Gaudio (first round)
 * 8) 🇷🇺 Marat Safin (final)