The 2023 Estoril Open (also known as the Millennium Estoril Open for sponsorship reasons) was a men's tennis tournament played on outdoor clay courts. It was the 8th edition of the tournament and part of the ATP Tour 250 series of the 2023 ATP Tour. It took place at the Clube de Ténis do Estoril in Cascais, Portugal, from 3 to 9 April 2023.[1]
See main article: 2023 Estoril Open – Singles.
Casper Ruud def. 
Miomir Kecmanović, 6–2, 7–6(7–3)See main article: 2023 Estoril Open – Doubles.
Sander Gillé / Joran Vliegen def. Nikola Ćaćić / Miomir Kecmanović, 6–3, 6–4| Event | W | F | SF | QF | Round of 16 | Round of 32 | width=85 | Q | width=85 | Q2 | width=85 | Q1 |
| Singles | 250 | 150 | 90 | 45 | 20 | 0 | 12 | 6 | 0 | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doubles | 0 |
| Event | W | F | SF | QF | Round of 16 | Round of 32 | width=85 | Q2 | width=85 | Q1 |
| Singles | €85,605 | €49,940 | €29,355 | €17,010 | €9,880 | €6,035 | €3,020 | €1,645 | ||
| Doubles* | €29,740 | €15,910 | €9,330 | €5,220 | €3,070 |
| Country | Player | Rank1 | Seed | |
|---|---|---|---|---|
| Norway | Casper Ruud | 4 | 1 | |
 Poland | Hubert Hurkacz | 9 | 2 | |
 Spain | Alejandro Davidovich Fokina | 25 | 3 | |
| Spain | Roberto Bautista Agut | 28 | 4 | |
 Argentina | Sebastián Báez | 33 | 5 | |
| Serbia | Miomir Kecmanović | 35 | 6 | |
| Argentina | Diego Schwartzman | 38 | 7 | |
 United States | Ben Shelton | 39 | 8 |
The following players received wildcards into the main draw:
The following players received entry as an emergency substitution:
The following players received entry from the qualifying draw:
Grégoire Barrère → replaced by Tseng Chun-hsin Pablo Carreño Busta → replaced by 
Dominic Thiem Sebastian Korda → replaced by Hubert Hurkacz Dušan Lajović → replaced by Jurij Rodionov
Emil Ruusuvuori → replaced by Luca Van Assche 
Mikael Ymer → replaced by 
Radu Albot| Country | Player | Country | Player | Rank1 | Seed | |
|---|---|---|---|---|---|---|
| Andreas Mies | Hugo Nys | 39 | 1 | |||
 Brazil | Marcelo Melo |  Australia | John Peers | 84 | 2 | |
 Ecuador | Gonzalo Escobar | France | Fabien Reboul | 97 | 3 | |
| Belgium | Sander Gillé | Belgium | Joran Vliegen | 101 | 4 |
The following pairs received wildcards into the doubles main draw:
Diego Hidalgo / 
Cristian Rodríguez 
Tomislav Brkić / Gonzalo Escobar → replaced by Gonzalo Escobar / Fabien Reboul 
Lloyd Glasspool / Harri Heliövaara → replaced by Andrew Harris / John-Patrick Smith Kevin Krawietz / Tim Pütz → replaced by 
Marco Cecchinato / Quentin Halys Rafael Matos / David Vega Hernández → replaced by Romain Arneodo / Sam Weissborn Jamie Murray / 
Michael Venus → replaced by Radu Albot / 
Victor Vlad Cornea Jan Zieliński → replaced by Andreas Mies / Hugo Nys