The Cathedral of the Holy Cross (Armenian: Սուրբ Խաչ եկեղեցի, romanized: Surp Khachʿ egeghetsʿi, Turkish: Akdamar Kilisesi or Surp Haç Kilisesi) on Aghtamar Island, in Lake Van in eastern Turkey, is a medieval Armenian Apostolic cathedral, built as a palatine church for the kings of Vaspurakan and later serving as the seat of the Catholicosate of Aghtamar.