Dalmatia (; Croatian: Dalmacija [dǎlmaːtsija]; Italian: Dalmazia [dalˈmattsja]; see names in other languages) is a historical region on the eastern shore of the Adriatic Sea in Croatia, a narrow belt stretching from the island of Rab in the north to the Bay of Kotor in the south. The Dalmatian Hinterland ranges in width from fifty kilometres in the north, to just a few kilometres in the south; it is mostly covered by the rugged Dinaric Alps. Seventy-nine islands (and about 500 islets) run parallel to the coast, the largest (in Dalmatia) being Brač, Pag, and Hvar. The largest city is Split, followed by Zadar, Šibenik, and Dubrovnik.

The name of the region stems from an Illyrian tribe called the Dalmatae, who lived in the area in classical antiquity. Later it became a Roman province, and as result a Romance culture emerged, along with the now-extinct Dalmatian language, later largely replaced with related Venetian. With the arrival of Croats to the area in the 6th century, who occupied most of the Hinterland, Croatian and Romance elements began to intermix in language and culture.

After the medieval Kingdom of Croatia entered a personal union with Hungary in 1102, its cities and lands were often conquered by, or switched allegiance to, the kingdoms of the region during the Middle Ages. At one time, most of Dalmatia came under rule of the Republic of Venice, which controlled most of Dalmatia between 1420 and 1797 as part of its State of the Sea, with the exception of the small but stable Republic of Ragusa (1358–1808) in the south. Between 1815 and 1918, it was a province of the Austrian Empire known as the Kingdom of Dalmatia. After the Austro-Hungarian defeat in World War I, Dalmatia was split between the Kingdom of Serbs, Croats and Slovenes, which controlled most of it, and the Kingdom of Italy, which held several smaller parts. After World War II, the People's Republic of Croatia as a part of Yugoslavia took complete control over the area. Following the dissolution of Yugoslavia, Dalmatia became part of the Republic of Croatia, and is today considered one of its four historical and cultural regions, alongside Croatia proper, Slavonia, and Istria.