The siege of Novi Zrin (New Zrin Castle); Croatian: Utvrda Novi Zrin; Hungarian: Új-Zrínyivár; Turkish: Zerinvar) in June/July 1664 was last of the military conflicts between the Croatian forces (with allies) led by Nikola Zrinski, Ban (viceroy) of Croatia, and the Ottoman army commanded by Köprülü Fazıl Ahmed Pasha, Grand Vizier, dealing with possession of Novi Zrin Castle, defended by Croats, situated on the bank and marshy islands of Mura River, near the border line between northern Croatia and southwestern part of Hungary, at the time occupied by the Ottomans. The battle resulted in destruction of the castle, and retreat of the Croatian crew, that was forced to withdraw to safer territory of inland Croatia.