Ostrvica or Ostrovica (Turkish: Sivrice Hisar)[1] was a small fortified town built on one of the peaks of Rudnik mountain, 4 kilometres (2.5 mi) northwest of the town of Rudnik.

In 1398 Nikola Zojić , a governor of Ostrovica,[6] retreated to Ostrvica after the failure of his attempt to overthrow Stefan Lazarević  and to establish direct vassalage to the Ottoman Empire.

[9] In 1414 voivode Mazarek is mentioned as a governor of Ostrvica and Rudnik.

[11][12] The Serbian despot recaptured it in 1443 during the Crusade of Varna, but the Ottomans captured it again in 1444, only to be restored to Serbia later in the year.

[13] Branković and Eirene used Ostrovica as their summer retreat, and had a mint in the castle.