Novi Zrin (Hungarian: Zrínyiújvár or Új-Zrínyivár) was a fortress of the Zrinski (Zrínyi in Hungarian) noble family built near the Donja Dubrava village in the northernmost part of Croatia (at the border village of Őrtilos in Hungary) on the mouth of river Mura into Drava between 1661 and 1664.
Its purpose was to stop the Ottoman military forces from advancing further into Croatia. The Ottomans attacked it several times from 1662 to 1664, but did not manage to conquer it. Finally, at the beginning of June 1664 a large Ottoman army, numbering up to 100,000 men, led personally by the Grand Vizier Köprülü Fazıl Ahmed Pasha, besieged it and destroyed on 7 July 1664.
Memorial obelisk on the place at the Mura River where the castle once was