Knin (pronounced [knîːn]) is a city in the Šibenik-Knin County of Croatia, located in the Dalmatian hinterland near the source of the river Krka, an important traffic junction on the rail and road routes between Zagreb and Split. Knin rose to prominence twice in history, as the capital of both the medieval Kingdom of Croatia and briefly of the self-proclaimed Republic of Serbian Krajina within the newly independent Republic of Croatia for the duration of the Croatian War of Independence from 1991 to 1995.

The name is likely derived from the Illyrian Ninia. According to an alternative explanation, offered by Franz Miklosich and Petar Skok, the name - derived from a Slavic root *tьn- ("to cut", "to chop") - means "cleared forest". The medieval names of Knin include Hungarian: Tinin; Italian: Tenin; Latin: Tinum. The Latin name is still used as a titular episcopal see, the Diocese of Tinum.

 Kingdom of Croatia (to 1102)
Kingdom of Croatia (union with Hungary), 1102–1522
Ottoman Empire, 1522–1688
Republic of Venice, 1688–1797
Holy Roman Empire, 1797–1805
First French Empire, 1805–1813
Austrian Empire, 1813–1867
 Austro-Hungarian Monarchy, 1867–1918
Kingdom of Yugoslavia, 1918–1941
Independent State of Croatia, 1941–1944
SFR Yugoslavia, 1944–1991
Republic of Serbian Krajina, 1991–1995
Croatia, 1995–present

The area consisting of today's Knin, or more specifically, the Spas hill, has been inhabited since the Stone Age. In the vicinity of today's Knin was once a town called Burnum, which served as a Roman military camp in the 1st century BC.

The original settlement grew atop the Spas hill in the earliest history and which later formed the castle of Knin. The first church, a monastery dedicated to Saint Bartholomew, was built during the time of Trpimir I in the 9th century in Kapitul (south-east from Knin Castle, where the later bishopric was located). It was later expanded or rebuilt by a certain Duke of Croatia, probably Svetoslav, during the reign of king Stephen Držislav of Croatia in the 10th century.

Knin is first mentioned in the 10th-century work De Administrando Imperio as the centre of the Knin county (županija), and as one of the populated towns in Croatia. Around 1040, at the behest of the Croatian kings, a seat of the royal bishop was established in the nearby royal village of Biskupija (Kosovo), in the church of Saint Mary. The first "bishop of the Croats" is named Marko Giudice, and he and his successors were attached to the royal court as preachers and king's "special bishops" until 1102.

Knin became a more permanent royal residence of king Demetrius Zvonimir around 1080. Because of this, it has led to Knin being known as the "City of Croatian Kings" or "Zvonimir's City" (Zvonimirov grad) in recent times. In the following decade, during the succession crisis, the city was the permanent residence of a local lord Petar Snačić, who contested the crown of Croatia until his defeat by king Coloman of Hungary in 1096. At that point, it came into possession of the Hungarian Arpad dynasty, and since then, it ceased to be a permanent royal residence but remained as a political and administrative center of the kingdom. The parish church dedicated to king Saint Stephen is thought to have been built during this period.

In 1178, it is for the first time mentioned as "civitates" (city) in a contemporary local source. Due to the extinction of the local ruling dynasty, the Croatian bishop moved his see to Knin itself, after which he started calling himself the Bishop of Knin. This precipitated the construction of a new cathedral, which was initiated in 1203 by the son of the Duke of Knin, Dobroslav in Kapitul.