The Cypriot-Turkish tactician has requested the club to relieve him from his duties after asking for five days of compassionate leave last week.
Oktay was appointed Gor Mahia's head coach in December 2018 to succeed Dylan Kerr, who had also resigned from his position after only one season.
“Kindly accept my resignation as Gor Mahia FC head coach effective today [August 6], the sixth day of August 2019. As you are aware, the decision has been forced on me by the personal challenges I am facing here in Europe," Oktay was quoted as saying by the club's website.
"I wish to thank you and the entire club, including the fans for the opportunity you accorded me to manage this great club. I also wish you guys all the best in your forthcoming assignments."
Subsequently, the club has accepted his resignation and thanked him for his services.
"The club has accepted Oktay’s wish to terminate his contract and thanks to him for his services. The club also prays for Oktay’s situation to get better," the club confirmed.
The club will also have to defend their KPL title without key players who helped them achieve a landmark 18th gong.
Jacques Tuyisenge left for Petro Atletico, Francis Kahata joined Simba SC while then-captain Harun Shakava has already penned a two-year contract with Nkana FC of Zambia.
Pascal Ogweno has been signed by KCB while George Odhiambo and midfielder Hashim Sempala are also on their way out.
Oktay's assistant coach Zedekiah Otieno has joined KCB as their head coach.