Tržan Castle in Modruš

Tržan Castle in Modruš Utvrda Tržan-grad u Modrušu
Modruš, Lika region, Croatia
Remains of Tržan Castle today
Tržan Castle in Modruš Utvrda Tržan-grad u Modrušu
Coordinates	45°07′41″N 15°14′28″E / 45.128°N 15.241°E / 45.128; 15.241
Type	Ridge castle
Site information
Controlled by	royal patronage possession (until 1193) , Frankopan noble family (1193–ca.1553) , Croatian Military Frontier headquarters (ca.1553–19th century)
Condition	ruined
Site history
Built	9th century
Built by	(unknown)
Materials	hewn stone (ashlar)

The Tržan Castle (Croatian pronunciation: [ˈtr̩̂ʒan]; Croatian: Tržan-grad or Utvrda Tržan) is a ruined medieval castle above the village of Modruš in the northern part of historical Lika region, central Croatia. Before (from the 11th century) the administrative seat of the former Modruš County (later renamed Modruš-Rijeka County), it is today just a ruin in the Josipdol Municipality in the southern part of the Karlovac County.

Having been built on a ridge of a steep hill 670 metres (2,200 ft) above sea level on the eastern slopes of the Velika Kapela mountain, the castle was at a strategic place overlooking the road that connected the Adriatic Sea and the Pannonian Basin since ancient times. The road in question connected the Roman towns of Senia (present-day Senj) and Siscia (present-day Sisak). It was later, during the 18th century, reconstructed, improved and renamed as Josephina road.

According to the famous Croatian historian Vjekoslav Klaić (1849–1928), a kind of a castle or stronghold most probably existed above Modruš already at the beginning of the 9th century, during a war between Borna, Duke of Dalmatian Croatia, and Ljudevit Posavski, Duke of Pannonian Croatia.