The 2015 Estoril Open (also known as the Millennium Estoril Open for sponsorship purposes) was a tennis tournament played on outdoor clay courts. The 2015 tournament was the first edition of the Estoril Open (which replaced the Portugal Open), and part of the ATP World Tour 250 series of the 2015 ATP World Tour. The event took place at the Clube de Ténis do Estoril in Cascais, Portugal, from April 25 through May 3, 2015.