The Germany striker, arguably the most famous soccer player in Turkey, issued a statement on his Facebook site explaining his reasons for a "difficult decision". He returns to parent club Fiorentina.
Mario Gomez could well be heading back to the Bundesliga after deciding the recent attempted coup in Turkey and its aftermath means it is not safe to stay playing for Istanbul side Besiktas.
"It was a difficult decision that I had to think about a lot. I have to tell you Besiktas fans personally that it is very heavy for me that I will not be playing for this great club in front of you wonderful fans in this unique stadium anymore," he wrote.
"The reason for this is completely down to the political situation! There are no sporting or any other reasons that have made me make this decision. It is purely down to the terrible events that happened in the last few days. I hope you can understand that!'
Former Bayern Munich frontman Gomez joined Besiktas in July last year on a season-long loan from Italian club Fiorentina but had been expected to stay after he finished up as the Turkish league's top scorer with 26 goals and his team won the title.
He will now return to Fiorentina but could easily be on the way back to the Bundesliga with over a month left in the transfer window. But it might not be the last we see of the 31-year-old in a Besiktas shirt.
"I hope that these political problems can be solved in a peaceful manner soon. Then it would be my great wish to play for Besiktas again!" he wrote.
"The club and the country grew very close to my heart in this past year. Hope to see you again soon."