The Estoril Open is an ATP and WTA clay court tournament held in Jamor, Oeiras, Portugal (in spite of nominally located in Estoril). The men's tournament was created in 1990 and since its inception, every champion except 2004 champion Juan Ignacio Chela has been in the Top 10 of the ATP rankings, including former world number one's Thomas Muster (1995 and 1996), Carlos Moyà (2000) and Juan Carlos Ferrero (2001). Also Marat Safin lost the 2004 final and Yevgeny Kafelnikov and Gustavo Kuerten won the doubles tournament in 1995 and 1997 respectively. It currently gives 40 Champion's Race points to its winner. The women's tournament, created in 1998, started as an ITF tournament, but in the next year became a WTA tournament. The women's tournament is less prestigious than the men's tournament, being a Tier IV.

Statistically, this tournament highlights the dominance of Argentine and Spanish male players on red clay. An Argentine has made the final at Estoril five of the last six finals (2002-2006); an Argentine won four of these five titles. Between 1990 and 2001, at least one Spaniard appeared in the final ten times, with a player from Spain claiming the title in nine of those twelve years.

On the women's side, in 2006 Estoril showcased the first all-Chinese final in tour history (between Jie Zheng and Na Li).