The 27-year-old, who has 46 caps and is in Turkey's 23-man squad for this month's European Championship in France, joins the Serie A club after six years with Fenerbahce.
Argentina midfielder Ever Banega is also set to join the Nerazzurri as a free agent in the summer transfer window.
Banega helped Sevilla lift the Europa League last season -- their third straight triumph -- to pick up his second winners' medal in Europe's second-tier competition.
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Banega said goodbye to his team mates after celebrating their success in the final against Liverpool last month.
"I still find it hard to speak about Sevilla in the past tense," he said in an interview this week with Spanish online newspaper ABCdesevilla (http://sevilla.abc.es).
"I talked to the guys... and of course it hurts. What I experienced in Seville was amazing. It will always be part of my life."
(Reporting by Silvia Recchimuzzi in Gdynia; editing by Ken Ferris)
