From the Wikipedia page 
Istanbul (UK: /ˌɪstænˈbʊl/, /-ˈbuːl/ or US: /-stɑːn-/; Turkish: İstanbul [isˈtɑnbuɫ] (About this sound listen)), historically known as Constantinople and Byzantium, is the most populous city in Turkey and the country's economic, cultural, and historic centre.
Since 2004, the municipal boundaries of Istanbul have been coincident with the boundaries of its province. The city, considered capital of Istanbul Province, is administered by the Istanbul Metropolitan Municipality (MMI), which oversees the 39 districts of the city-province.
The current city structure can be traced back to the Tanzimat period of reform in the 19th century, before which Islamic judges and imams led the city under the auspices of the Grand Vizier. Following the model of French cities, this religious system was replaced by a mayor and a citywide council composed of representatives of the confessional groups (millet) across Istanbul. Beyoğlu was the first area of the city to have its own director and council, with members instead being longtime residents of the neighborhood. Laws enacted after the Ottoman constitution of 1876 aimed to expand this structure across the city, imitating the twenty arrondissements of Paris, but they were not fully implemented until 1908, when Istanbul was declared a province with nine constituent districts. This system continued beyond the founding of the Turkish Republic, with the province renamed a belediye (municipality), but the municipality was disbanded in 1957.