The 1990 Estoril Open was a combined men's and women's tennis tournament played on outdoor red clay courts.

It was the first edition of the event Estoril Open for the men (the 2nd for the women), and was part of the ATP World Series of the 1990 ATP Tour.

It took place at the Estoril Court Central, in Oeiras, Portugal, from 2 April through 8 April 1990 for the men's tournament and from 16 July through 22 July 1990 for the women's tournament.

Emilio Sánchez and Federica Bonsignori won the singles titles.

Emilio Sánchez defeated Franco Davín 6–3, 6–1 Federica Bonsignori defeated Laura Garrone 2–6, 6–3, 6–3 Sergio Casal / Emilio Sánchez defeated Omar Camporese / Paolo Canè 7–5, 4–6, 7–5 Sandra Cecchini / Patricia Tarabini defeated Carin Bakkum / Nicole Jagerman 1–6, 6–2, 6–3