Istanbul High School (Turkish: İstanbul Lisesi, German: Istanbuler Gymnasium), also commonly known as Istanbul Boys' High School (Turkish: İstanbul Erkek Lisesi, abbreviated İEL), is one of the oldest and internationally renowned high schools of Turkey. The school is considered elite among Turkish public high schools. Germany recognizes the school as a Deutsche Auslandsschule (German International school).

Istanbul High School is located in Cağaloğlu, İstanbul. The school has changed several buildings throughout its history. Since 1933 the school has used its current building. The building was designed by architects Alexander Vallaury and Raimondo D'Aronco and inaugurated in 1882 as the Düyun-u Umumiye (Council of Ottoman Revenues and Debts Administration) Building, which overlooks the entrance to the Bosphorus and the Golden Horn. A new building adjacent to the main historical building was inaugurated in 1984, providing new boarding and sports facilities. The primary languages of instruction are Turkish and German. The secondary foreign language of instruction is English.