Gli the Hagia Sophia cat died at the age of 16 on Nov. 7, months after the site was converted into a mosque.
His caretakers in September had announced that he fell ill and that he had been living in a private room away from people.
"I was born in Hagia Sophia, the heart of the world. I met with millions of people who visited the heart of the world and became a mirror for the light of love. I died," read the caption of the post on his Instagram account on Nov. 7.
"I thank everyone who carry the marks of my paws in their hearts," it added.
Gli's caretakers had been sharing footage of his treatment in a veterinary clinic.
Before his isolation, the caretakers warned worshippers to not overwhelm Gli after footage of them taking pictures of the cat with flashes and feeding him unhealthy food emerged on social media.Gli the Hagia Sophia cat falls ill two months after the site's conversion into a mosque
Muslims were also seen to be putting on Ottoman clothing on the cat despite repeated warnings on not to touch him.
Hagia Sophia was opened for worship on July 24 after it was declared a mosque by President Recep Tayyip Erdoğan.
Following the site's conversion, Islamists and pro-government trolls on Twitter had also started to search for a new name for Gli, saying that it should be more Islamic.
Yakışmış ? pic.twitter.com/lgZvvc6K4w— Mehmet Ardıç ???? (@MehmetArdic_) July 24, 2020
Istanbul Governor Ali Yerlikaya on Nov. 7 shared the news on Twitter, saying that Gli died of old age.
Gli’yi kaybetmenin üzüntüsünü yaşıyorum.— Ali Yerlikaya (@AliYerlikaya) November 7, 2020
24 Eylül tarihinden beri Levent'teki özel bir veteriner kliniğinde tedavi gören #Ayasofya’nın kedisi Gli yaşlılığa bağlı olarak maalesef yaşamını yitirdi.?
Seni hiç unutmayacağız #Gli ?#AyasofyaCami pic.twitter.com/Ly6IXsEMHJ
"Gli, who had been receiving treatment at a private veterinary clinic in Levent since Sept. 24, died of old age. We will never forget you," he said.
Turkish Presidential Spokesperson İbrahim Kalın quoted Yerlikaya's tweet and said, "Beautiful Gli" with a sad face emoji.
Güzel Gli? https://t.co/v14hHqT5ns— Ibrahim Kalin (@ikalin1) November 7, 2020