Modruš is a village, former episcopal see, and current Latin Church Catholic titular see in the mountainous part of Croatia, located south of its municipality's seat Josipdol (Karlovac County), on the easternmost slopes of Velika Kapela mountain, in northern Lika.

The population was 169 in the census of 2011.

One of the counties in the Kingdom of Croatia-Slavonia (an autonomous kingdom within the Hungarian part of Austria-Hungary) was named Modruš-Rijeka County partially after the town.

The fortress may have already existed in 1209. The town around it developed during the 14th and 15th centuries.

From 1193 until 1553 Modruš and the large surrounding estate was owned by members of the Frankopan noble family, who were living in the Tržan castle above the medieval settlement.

In 1460, Modruš became the seat of the Roman Catholic Diocese of Krbava-Modruš.

Modruš was mentioned on 22 February 1481 in a document freeing the citizens of Grič from tariffs in Modruš and elsewhere.

In 1553, Modruš came under the administration of the Military Frontier authorities.