2018 Estoril Open

The 2018 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 fourth edition of the Estoril Open, and part of the ATP World Tour 250 series of the 2018 ATP World Tour. The event took place at the Clube de Ténis do Estoril in Cascais, Portugal, from April 30 through May 6, 2018.

Seeds

 * Rankings are as of April 23, 2018.

Other entrants
The following players received wildcards into the singles main draw:
 * 🇦🇺 Alex de Minaur
 * Frederico Ferreira Silva
 * Pedro Sousa

The following players received entry from the qualifying draw:
 * 🇮🇹 Simone Bolelli
 * João Domingues
 * 🇪🇸 Ricardo Ojeda Lara
 * 🇺🇸 Tim Smyczek

Withdrawals

 * Before the tournament
 * 🇪🇸 David Ferrer → replaced by 🇬🇧 Cameron Norrie
 * 🇦🇺 Nick Kyrgios → replaced by 🇦🇷 Nicolás Kicker
 * 🇫🇷 Benoît Paire → replaced by Gastão Elias

Seeds

 * Rankings are as of April 23, 2018.

Other entrants
The following pairs received wildcards into the doubles main draw:
 * 🇦🇺 Alex de Minaur / 🇦🇺 Lleyton Hewitt
 * Gastão Elias / Pedro Sousa

Singles

 *  João Sousa def. 🇺🇸 Frances Tiafoe, 6–4, 6–4

Doubles

 * 🇬🇧 Kyle Edmund / 🇬🇧 Cameron Norrie def. Wesley Koolhof / 🇳🇿 Artem Sitak, 6–4, 6–2