Rumelihisarı (also known as Rumelian Castle and Roumeli Hissar Castle) is a fortress located in the Sarıyer district of Istanbul, Turkey, on a hill at the European Side of the Bosphorus. It gives the name of the quarter around it. It was built by the Ottoman Sultan Mehmed II between 1451 and 1452, before he conquered Constantinople. The three great towers were named after three of Mehmed II's viziers, Sadrazam Çandarlı Halil Pasha, who built the big tower next to the gate, Zağanos Pasha, who built the south tower, and Sarıca Pasha, who built the north tower.
In 1953, on the orders of President Celal Bayar, the inhabitants were relocated and extensive restoration work began on 16 May 1955, which lasted until 29 May 1958. Since 1960 Rumelihisarı has been a museum and an open-air theater for various concerts at festivals during the summer months.
The Fatih Sultan Mehmet Bridge which spans the Bosporus is located close to the fortress, to the north. Rumelihisarı is open to public every day except Wednesdays from 9:00 to 16:30. The fortress was depicted on various Turkish banknotes during 1939-1986.