Srb (Срб) is a village located in the southeastern part of Lika, in Croatia, till 2011 administratively divided into Donji Srb (population 255, census 2001) and Gornji Srb (population 79, census 2001). Srb lies in the Una River valley, on the road from Donji Lapac to Knin, and is east of Gračac. It is currently part of the Gračac municipality and the Zadar County.
According to Croatian linguist and academic Petar Šimunović, etymologically it is a hydronym that derives from the old Croatian verb "serbati" denoting the "spring" of the river Una. Because Serbs (Sorabos) are mentioned in the Royal Frankish Annals in the context of Ljudevit Posavski fleeing to them, there is a theory that a Serbian tribe could have existed in the area of Srb at some point in the 9th century, and that Srb was named after them, but the scarcity of historical records made various historians differ in the interpretations of this mention. That account most probably refers to somewhere in central or eastern Bosnia.
In the medieval period, the settlement was the centre of small župa of Srb which was part of a larger župa of Pset of the Duchy and Kingdom of Croatia. In the 13th and 14th century the župa was ruled by Paul I Šubić of Bribir and Nelipić family.
In the 14th century is mentioned as a town because a document from the year 1345 mentions it belonging to the Hungary-Croatian king as a royal fortress-citadel, castra nostra regalia, videlicet Tininium ... castrum Szereb ... castrum Unach vocata cum Corum supatibus et pertinensiis. This town was built on a hill high above the stream Sredice, where its remains still stand today. The župa had a noble court table of at least three judges, and although župans possibly were from the old Croatian noble tribe of Gusić, the Croatian nobles (plemenitimi H'rvati) from the presumed tribe of Srbljani mentioned in 1451 were Marko and Martin Dijanišević, Juraj Henčić, Vojin Matijašević, Vlatko Anić and Jandrij Kovač.
Due to the Ottoman conquest in 1520, most of the old population fled to Northern Croatia and was replaced by pastoral Vlachs.