Karolína Plíšková was the defending champion; she chose, however, not to defend her title.
Lu Jingjing was the defending champion, but lost to the 3rd seeded Tetiana Luzhanska in the first round.
An-Sophie Mestach and Demi Schuurs were the defending champions but neither of them were eligible to participate in 2012. American couple Gabrielle Andrews and Taylor Townsend won the title, defeating Irina Khromacheva and Danka Kovinić in the final, 5–7, 7–5, [10–6].
This was the first edition of the event. Kurumi Nara won the title, defeating Klára Zakopalová in the final, 6–1, 4–6, 6–1.
Paula Ormaechea was the defending champion, having won the event in 2013, but decided to compete at the Internazionali BNL d'Italia instead.
Agnieszka Radwańska was the defending champion, but lost to Varvara Lepchenko in the quarterfinals.
Andrea Petkovic was the defending champion, but she lost to Angelique Kerber in the semifinals.
Heather Watson was the defending champion, but lost to Polona Hercog in the first round.
Danka Kovinić was the defending champion, but she lost in the first round to Tessah Andrianjafitrimo.
Lesia Tsurenko was the defending champion, but lost in the first round to Sorana Cîrstea.
Daria Gavrilova and Elina Svitolina were the defending champions, but chose not to participate this year.
Andreea Mitu and İpek Soylu won the title by walkover when Xenia Knoll and Danka Kovinić withdrew from the final. Mitu and Soylu won the title by playing only two matches, since their semifinal opponents also withdrew.
Monica Niculescu was the defending champion, but chose not to participate.
Han Xinyun was the defending champion, but lost in the quarterfinals to Jamie Loeb.
Danka Kovinić was the defending champion, but lost in the first round to Tessah Andrianjafitrimo.
Johanna Konta was the defending champion after winning the last event in 2015, but chose to participate in Cincinnati instead.
Christina McHale was the defending champion, but lost in the semifinals to Zarina Diyas.
Risa Ozaki was the defending champion, but chose to compete in Tokyo instead.
Markéta Vondroušová was the defending champion, but lost in the second round to Elise Mertens.
The 2018 Istanbul Cup - Singles was won by Pauline Parmentier after defeating Polona Hercog in the final match, 6–4, 3–6, 6–3. Elina Svitolina, the defending champion, chose to compete in Stuttgart instead.
Anastasia Pavlyuchenkova was the defending champion, but chose not to participate.
