1990 Estoril Open – Women's singles

Isabel Cueto was the defending champion, but lost in the quarterfinals to Federica Bonsignori.

Bonsignori won the title by defeating Laura Garrone 2–6, 6–3, 6–3 in the final.

Seeds
• # Isabel Cueto (quarterfinals)

• # 🇮🇹 Sandra Cecchini (second round)

• # Sabine Hack (semifinals)

• # Nicole Jagerman (second round)

• # Angeliki Kanellopoulou (second round)

• # 🇦🇷 Patricia Tarabini (semifinals)

• # Petra Langrová (first round)

• # 🇦🇷 Florencia Labat (second round)