Sayaka Ishii (石井さやか, Ishii Sayaka, born 31 August 2005) is a Japanese professional tennis player. She has career-high rankings of world No. 203 in singles, achieved on 28 October 2024, and No. 345 in doubles, achieved on 21 October 2024.
In July, she and compatriot Naho Sato won the doubles title at the Figueira da Foz International Ladies Open.[5] The following month, she made her WTA Tour debut after qualifying for Tennis in the Land.[6] She lost to third seed Kateřina Siniaková in three sets.[7] In October, she qualified for her second main draw at the Toray Pan Pacific Open with a defeat over top qualifying seed Clara Tauson. She then recorded her first WTA Tour wins over compatriot and lucky loser Sara Saito[8][9][10] and qualifier Zeynep Sönmez to reach her first WTA 500-level quarterfinal.[11][12][13][14] Ishii withdrew with an abdominal injury before her last eight match with sixth seed Diana Shnaider.[15][16][17] As a result she reached a new career-high, three spots shy of the top 200 on 28 October 2024 raising close to 80 positions up in the singles rankings, having been ranked No. 279 in the beginning of the tournament.[18]