"I won't be Besiktas' manager next season. I'm proud of what I've done here," Bilic told reporters after Sunday's 2-0 derby loss to Galatasaray saw Besiktas miss out on Champions League qualification.
"As I said before, I am the first one who is going to take responsibility for not winning the league for two years. I have already made my decision."
A fan favourite, Bilic has been working with Besiktas since June 2013.
Bilic spent six successful years with the Croatia national team and then took over at Dynamo Moscow for one season before signing as Besiktas coach.
The 46-year-old spent a little more than a year at Upton Park as a player from 1996, making over 40 appearances for West Ham.

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