The 2017 Estoril Open (also known as the Millennium Estoril Open for sponsorship purposes) was a professional men's tennis tournament played on outdoor clay courts. It was the third edition of the Estoril Open, and part of the ATP World Tour 250 series of the 2017 ATP World Tour. The event took place at the Clube de Ténis do Estoril in Cascais, Portugal, from 29 April to 7 May 2017.
Singles main-draw entrants
Seeds
| Country | Player | Rank1 | Seed |
|---|---|---|---|
 ESP
|
Pablo Carreño Busta | 20 | 1 |
 FRA
|
Richard Gasquet | 23 | 2 |
 LUX
|
Gilles Müller | 28 | 3 |
| ESP
|
David Ferrer | 32 | 4 |
 ARG
|
Juan Martín del Potro | 33 | 5 |
 POR
|
João Sousa | 37 | 6 |
 GBR
|
Kyle Edmund | 42 | 7 |
| FRA
|
Benoît Paire | 49 | 8 |
- Rankings are as of April 24, 2017.
Other entrants
The following players received wildcards into the singles main draw:
The following players received entry using a protected ranking into the singles main draw:
The following players received entry from the qualifying draw:
Withdrawals
- Before the tournament
- Federico Delbonis →replaced by Guillermo García López
Nick Kyrgios →replaced by Renzo Olivo
Daniil Medvedev →replaced by Evgeny Donskoy- Juan Mónaco →replaced by Gastão Elias
Yoshihito Nishioka →replaced by 
Kevin Anderson- Albert Ramos Viñolas →replaced by Yūichi Sugita
- During the tournament
Doubles main-draw entrants
Seeds
| Country | Player | Country | Player | Rank1 | Seed |
|---|---|---|---|---|---|
| AUS
|
Sam Groth |  SWE
|
Robert Lindstedt | 95 | 1 |
 NED
|
Wesley Koolhof | NED
|
Matwé Middelkoop | 101 | 2 |
 NZL
|
Marcus Daniell |  BRA
|
Marcelo Demoliner | 102 | 3 |
 IND
|
Leander Paes | BRA
|
André Sá | 114 | 4 |
- Rankings are as of April 24, 2017.
Other entrants
The following pairs received wildcards into the doubles main draw:
Champions
Singles
- Pablo Carreño Busta def. Gilles Müller, 6–2, 7–6(7–5)
Doubles
Ryan Harrison / Michael Venus def. David Marrero / Tommy Robredo, 7–5, 6–2