Naval High School (Turkish: Deniz Lisesi); known in the Ottoman period as the Imperial School of Naval Engineering (Mühendishane-i Bahr-i Hümâyûn) and later as the Imperial Naval School (Mekteb-i Bahriye-i Şahane); is a Turkish naval high school located on Heybeliada Island (the second largest of the Prince Islands) in the Sea of Marmara, to the southeast of Istanbul, Turkey. After the 2016 Turkish coup d'état attempt, the Naval High School, along with the other military high schools in Turkey, was closed. Subsequently, the National Defense University was established in 2016.