Religion in Istanbul covers the issue of religion in the city of Istanbul, Turkey. More than 90% of Istanbul's population are Sunni Muslims and Alevism forms the second biggest religious group. A 2019 survey study by KONDA that examined the religiosity of the voting-age adults in Istanbul showed that 57% of the surveyed had a religion and were trying to practise its requirements. This was followed by nonobservant people with 26% who identified with a religion but generally did not practise its requirements. 11% stated they were fully devoted to their religion, meanwhile 6% were non-believers who did not believe the rules and requirements of a religion. 24% of the surveyed also identified themselves as "religious conservatives".