Halych-Volhynia, or Halych-Volodymyr, was a large state in Ruthenia (Rus' ) which existed in the 13th and 14th centuries. It extended between the rivers San and Wieprz in what is now south-eastern Poland in the west, and the Pripet Marshes (now in Belarus) and upper Southern Bug in modern-day Ukraine in the east. It was the major Eastern Slavic power after the collapse of Kievan Rus'.

Halych-Volhynia was created by Prince Roman Mstislavich of Volodymyr-Volhynia after he conquered the Principality of Halych and united both lands into one state at the end of 12th century. Its principal cities were Halych and Volodymyr-Volyns'kyi. With the help of wealthy burghers, some loyal boyars and Polish princes, he created a relatively strong power, subjecting Kiev to his domination and increasing Ruthenian influence in Lithuania. He also signed a peace treaty with Hungary and developed diplomatic relations with the Byzantine Empire.

In 1205 he turned against his Polish allies which led to a conflict with Leszek the White and Konrad of Masovia. Roman was subsequently killed in the battle of Zawichost (1205) and his dominion broke up into a number of independent principalities. The weakened Halych-Volhynia became an arena of rivalry between Poland and Hungary. King Andrew II of Hungary styled himself rex Galiciae et Lodomeriae, Latin for "king of Halych and Volodymyr". In a compromise agreement made in 1214 between Hungary and Poland, the throne of Halych-Volhynia was given to Andrew's son, Coloman who had married Leszek the White's daughter, Salomea.

In 1221, Mstislav the Bold , son of Mstislav the Brave , liberated Halych-Volhynia from the Hungarians, but it was Danylo, son of Roman, who re-united all of south-western Ruthenia, including Volhynia, Halych and Kiev. Danylo defeated the Polish and Hungarian forces in the battle of Yaroslav (Jarosław) in 1245, but at the same time he was compelled to acknowledge, at least nominally, the supremacy of the Tatar Golden Horde. In 1245, Pope Innocent IV allowed Danylo to be crowned king, although his realm continued to be ecclesiastically independent from Rome.

Under Danylo's reign, Halych-Volhynia was a powerful and thriving state. Literature flourished, producing the Halych-Volhynian Chronicle. Demographic growth was enhanced by immigration from the west and the south, and commerce developed thanks to trade routes linking the Black Sea with Poland, Germany and the Baltic basin. Major cities, which served as important economic and cultural centers, were among others: L'viv (where the royal seat was moved), Volodymyr, Halych, Kholm, Peremyshl, Dorohychyn and Terebovlya . At the peak of its expansion, the Halych-Volhynian state contained not only all south-western Ruthenia, including Red Ruthenia and Black Ruthenia, but also briefly controlled Bessarabia and Moldavia.

After King Danylo's death in 1264, his kingdom broke up once again. Although nominally ruled by Danylo's sons, it was in fact controlled by the boyars. In 1352 the principality was eventually divided between Poland and Lithuania. King Casimir the Great of Poland took Halych, Belz, Kholm, Podolia and part of Volhynia; Gediminas of Lithuania took the remaining part of Volhynia and Podlachia.

By the treaty of the Lublin Union of 1569, all of former Halych-Volhynia became part of Poland. In 1772, Empress Maria Theresa of Austria (who was also Queen of Hungary) recalled the old Hungarian claims to the Regnum Galiciae et Lodomeriae, and used them to justify Austria's participation in the partitions of Poland. Polish territories taken by Austria were, therefore, officially named Galicia and Lodomeria, even though they did not correspond exactly to the historical lands of Halych-Volhynia. Despite the fact that the title derived from the historical Hungarian crown, Galicia and Lodomeria was not officially assigned to Hungary, and after the Ausgleich of 1867, it found itself in Cisleithania, the Austrian part of Austria-Hungary.

See also

• History of Ukraine
• List of early East Slavic states