2003 Estoril Open – Men's singles

David Nalbandian was the defending champion but did not compete that year.

Nikolay Davydenko won in the final 6–4, 6–3 against Agustín Calleri.

Seeds

 * 1) 🇨🇿 Jiří Novák (first round)
 * 2) 🇩🇪 Rainer Schüttler (first round)
 * 3)  Sjeng Schalken (first round)
 * 4)  Fernando González (quarterfinals)
 * 5) 🇪🇸 Tommy Robredo (semifinals)
 * 6) 🇷🇺 Yevgeny Kafelnikov (quarterfinals)
 * 7) 🇧🇾 Max Mirnyi (semifinals)
 * 8) 🇫🇮 Jarkko Nieminen (second round)