Sarıyer (pronounced [saˈɾɯjeɾ]) is a municipality and district of Istanbul Province, Turkey. Its area is 177 km² and its population is 350,454 (2022). It is on the northeastern part of Istanbul's European side. Sarıyer also administers the Black Sea coast to the west of the mouth of the Bosphorus, including the neighbourhood of Kilyos. It borders Eyüpsultan to the northwest, Beşiktaş to the south and Kağıthane to the west. The mayor is Mustafa Oktay Aksu of the Republican People's Party (CHP).

It is the site of the ancient Greek city of Phinopolis (Greek: Φινούπολις), which was founded on an existent Thracian settlement. Sarıyer's Bosphorus villages, backed by steep hills, were once rural fishing communities. In the 18th century, palace officials and other people close to the Ottoman sultan started building their yalıs on the coastline. Around this time, wealthy foreign traders of Pera and Galata built summer residences in the area. In the beginning of the 19th century, the embassies, located in Istanbul proper, started acquiring plots of lands to build summer residences. Despite all this development, the villages remained quiet fishing towns up until the 1950s. In the 1950s and 60s, the Sarıyer villages were considered "holiday towns" for the people living in Istanbul. However, since the construction of the coast road, these villages, and increasingly the hillsides behind them, rapidly urbanized. By the 1980s, the coastal areas were full of newly built, expensive apartments, while the hillsides being built up with illegal housing called gecekondu.

The district Sarıyer was established in 1930 from parts of the districts of Beyoğlu and Çatalca. The district's boundaries shrunk after the neighbourhood of Kemerburgaz was given to the Eyüp district in 1936 and when the villages of Maslak and Ayazağa were given to Şişli district in 1954. The present boundaries of Sarıyer were created after incorporating the neighbourhoods of Maslak, Ayazağa and Huzur from the district of Şişli in 2012.

There are 38 neighbourhoods in Sarıyer District:

Sarıyer is connected to downtown Istanbul by Büyükdere Avenue, the main road from Beşiktaş up to Maslak and beyond; this is the route used by minibuses serving Sarıyer-Beşiktaş. There is also high-speed ferry boat service for commuting to the city. The M2 metro line runs via Maslak to Hacıosman. However, many people commute by car, contributing to the heavy traffic congestion.

Sarıyer itself is a traditional working-class Turkish town, lacking in infrastructure. The industry feeds the local fish market and a long line of famous fish restaurants. There are also a variety of cafés, kebab houses and bars, where many of İstanbul's residents come to eat and drink on weekends.

Emirgan is former retreat from the city, backed by a hillside still green despite the recent construction of villas within it. The district is named after Emir Güne Han, a Persian nobleman who was given 50 hectares of land in the area in 1635 by Murad IV after he surrendered Yerevan without a fight. There is a square in the center, shaded by a huge plane tree, with a cafe in the middle. It is home to the Sakıp Sabancı Museum. Emirgan Korusu, which hosts the Emirgan Tulip Festival annually, is also located in the neighborhood.

Reşitpaşa is a crowded district on the hill above Emirgan. It has both attractive villas and illegal gecekondu housing on a forested hillside. The modern campus of the Istanbul Stock Exchange is nearby, along with one of the campuses of Istanbul Technical University.