Silivri, formerly Selymbria (Greek: Σηλυμβρία), is a municipality and district of Istanbul Province, Turkey. Its population is 217,163 (2022). It lies along the Sea of Marmara, outside the urban core of Istanbul, containing many holiday and weekend homes for residents of the city. The largest settlement in the district is also named Silivri.
Silivri is located bordering Büyükçekmece to the east, Çatalca to the north, Çorlu and Marmara Ereğlisi (both districts of Tekirdağ Province) to the west, Çerkezköy to the north-west (one of Tekirdağ Province) and with the Sea of Marmara to the south. It is, with an area of 858 km (331 sq mi), the second largest district of Istanbul Province after Çatalca. The seat of the district is the city of Silivri.