Zadar is the oldest continuously inhabited Croatian city. It is situated on the Adriatic Sea, at the northwestern part of Ravni Kotari region. Zadar serves as the seat of Zadar County and of the wider northern Dalmatian region. The city is the second-largest city of the region of Dalmatia and the fifth-largest city in the country.

The area of present-day Zadar traces its earliest evidence of human life from the late Stone Age, while numerous settlements date as early as the Neolithic.[citation needed] Before the Illyrians, an ancient Mediterranean people of an Indo-European culture inhabited the area. Zadar traces its origin to its 9th-century BC founding as a settlement of the Illyrian tribe of Liburnians known as Iader.

In 59 BC it was renamed Iadera when it became a Roman municipium. In 48 BC it became a Roman colonia. During Roman rule Zadar acquired the characteristics of a traditional Ancient Roman city with a regular road network, a public square (forum), and an elevated capitolium with a temple.

After the fall of the Western Roman Empire in 476 and the destruction of Salona by the Avars and Croats in 614, Zadar became the capital of the Byzantine theme of Dalmatia. In the beginning of the 9th century, Zadar came briefly under Frankish rule, but the Pax Nicephori returned it to the Byzantines in 812. The first Croatian rulers gained brief control over the city in 10th century. In 998 Zadar swore allegiance to Doge Pietro Orseolo II and became a vassal of the Republic of Venice. In 1186 it placed itself under the protection of Béla III, King of Hungary and Croatia.

In 1202 the Venetians, with the help of Crusaders, reconquered and sacked Zadar. Hungary regained control over the city in 1358, when it was given to king Louis I of Hungary. In 1409 king Ladislaus I sold Zadar to the Venetians. When the Ottoman Empire conquered the Zadar hinterland at the beginning of the 16th century, the town became an important stronghold, ensuring Venetian trade in the Adriatic, the administrative center of the Venetian territories in Dalmatia and a cultural center. This fostered an environment in which arts and literature could flourish, and between the 15th and 17th centuries Zadar came under the influence of the Renaissance, giving rise to many important Italian Renaissance figures like Giorgio Ventura and Giovanni Francesco Fortunio, who wrote the first Italian grammar book, and many Croatian writers, such as Petar Zoranic, Brne Krnarutic, Juraj Barakovic and Šime Budinic, who wrote in the Croatian language.

After the fall of Venice in 1797, Zadar came under the Austrian rule until 1918, except for the period of short-term French rule (1805-1813), still remaining the capital of Dalmatia. During French rule the first newspaper in the Croatian language, Il Regio Dalmata - Kraglski Dalmatin, was published in Zadar (1806–1810). During the 19th century Zadar functioned as a center of the Croatian movement for cultural and national revival in a context of increasing polarization and politicization of ethnic identities between Croats and Dalmatian Italians.

With the 1920 Treaty of Rapallo Zadar was given to the Kingdom of Italy. During World War II, it was bombed by the Allies and witnessed the evacuation of ethnic Italians. Partisans captured the city on 1 November 1944; in 1947 it officially became part of SR Croatia, a federal constituent of the SFR Yugoslavia, whose armed forces defended it in October 1991 from the Serb forces who aimed to capture it.

Today, Zadar is a historical center of Dalmatia, Zadar County's principal political, cultural, commercial, industrial, educational, and transportation centre. Zadar is also the seat of the Roman Catholic Archdiocese of Zadar. Because of its rich heritage, Zadar is today one of the most popular Croatian tourist destinations, named "entertainment center of the Adriatic" by The Times and "Croatia's new capital of cool" by The Guardian. In 2016 the Belgian portal Europe's Best Destinations.com named Zadar the "Best European Destination" after a three-week period of online voting involving more than 288,000 votes.

UNESCO's World Heritage Site list included the fortified city of Zadar as part of Venetian Works of Defence between 15th and 17th centuries: Stato da Terra - western Stato da Mar in 2017.