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.

The following players received wildcards into the singles main draw: The following players received entry from the qualifying draw: The following pairs received wildcards into the doubles main draw: