Learn more about Istria with breef Istrian History overview
Istria name comes from ancient autochtonous inhabitants of the peninsula, the so-called Histrians, who lived in this area from 800 to 500 B.C.
During the past century Istria was under the influence of different countries and cultures.
The Romans, Greeks, Slavs, Venetians and the Habsburgs ruled Istria and in different ways influenced the culture of the Istrian peninsula.
Some scholars speculate that the names Histri and Istria are related to the Latin name Hister, or Danube.
Ancient folktales reported—inaccurately—that the Danube split in two or "bifurcated" and came to the sea near Trieste as well as at the Black Sea. The story of the "Bifurcation of the Danube" is part of the Argonaut legend.
After the fall of the Western Roman Empire, the region was pillaged by the Goths, the Eastern Roman Empire, and Avars, annexed to the Lombards Kingdom in 751, annexed to the Frankish kingdom by Pippin III in 789, and then successively controlled by the counts of Carantania, Meran, Bavaria and by the patriarch of Aquileia, before it became the territory of the Venetian Republic in 13th century.
During centuries Istria was under so many different rulers. 
Here is a list of them with short descriptions:
Venetian Republic and the Holy Roman Empire
The coastal areas and cities of Istria came under Venetian Influence in the IX century, It became definitely the territory of the Republic of Venice in 1267. The Inner Istrian part around Mitterburg (Pazin), was held for centuries by the Holy Roman Empire.
Austrian Empire (1797-1805)
Venetian rule left a strong mark on the region, one that can still be seen today. The Inner Istrian part around Mitterburg, was held for centuries by the Holy Roman Empire. The venetian part of the peninsula passed to it in 1797 with the Treaty of Campo Formio.
Italian Kingdom (Napoleon Empire) 1805-1813
The Holy Roman Empire ended with the period of Napoleonic rule from 1805 to 1813 when Istria became part of the Italian Kingdom and of the Illyrian provinces of the Napoleonic Empire.
Austrian Empire (1814-1918)
After this short period the newly established Austrian Empire ruled Istria as the so called "Küstenland" which included the city of Trieste and Gorizia in Friuli until 1918. At that time the borders of Istria included a part of what is now Italian Venezia-Giulia and parts of modern-day Slovenia and Croatia, but not the city of Trieste. Today, Istria's borders are defined differently.
Kingdom of Italy 1918-1945
Istria under Italian rule (1918-1945). Fascism took over in Italy in 1922, four years after Istria was annexed.
After World War I and the dissolution of Austria-Hungary, Istria was given to Italy. After the advent of Fascism, the portions of the Istrian population that were Croatian and Slovene were exposed to a policy of forced Italianization and cultural suppression. They lost their right to education and religious practice in their maternal languages. The organization TIGR, regarded as the first armed antifascist resistance group in Europe, was founded in 1927 and soon penetrated into Slovene and Croatian-speaking parts of Istria.
SFR Yugoslavia 1945-1991
After the end of World War II, Istria was included into Yugoslavia, except for a small part in the northwest corner that formed Zone B of the provisionally independent Free Territory of Trieste (Trst); Zone B was under Yugoslav administration and after the de facto dissolution of the Free Territory in 1954 it was also incorporated into Yugoslavia. Only the small town of Muggia (Milje), near Trieste, being part of Zone A remained with Italy.
The events of that period are visible in Pula. The city had an Italian majority, and is located on the southernmost tip of the Istrian peninsula. Between December 1946 and September 1947, a large proportion of the city's inhabitants emigrated to Italy. Most of them left in the immediate aftermath of the signing of the Paris Peace Treaty on February 10, 1947, which granted Pula to Yugoslavia. After 1954, the border between the Slovenia and Croatia ran along along the river Mirna. According to the Croatian historiographer Stjepan Srkulj, this is the first time in Croatian history that Istria has been under Croatian jurisdiction.
After the breakup of Yugoslavia - after 1991 
The division of Istria between Croatia and Slovenia runs on the former republic borders, which were not precisely defined in the former Yugoslavia. Various bones of contention remain unresolved between the two countries regarding the precise line of the border. It became an international boundary with the independence of both countries from Yugoslavia in 1991. Since Croatia's first multi-party elections in 1990, the regional party Istrian Democratic Assembly (IDS-DDI, Istarski demokratski sabor or Dieta democratica istriana) has consistently received a majority of the vote and maintained through 1990s a position often contrary to the government in Zagreb.