Sandalj Hranić Kosača was a powerful Bosnian nobleman whose primary possessions consisted of land areas between Adriatic coast, the Neretva and the Drina rivers in Bosnia, and served the court as the Grand Duke of Bosnia sometime between 1392 and his death in 1435, although the first mention as a Grand Duke in sources comes from 16 June 1404. He was married three times, but had no children. After his death, he was succeeded by his nephew Stjepan Vukčić Kosača.

The history of Bosnia and Herzegovina in the Middle Ages refers to the time period between the Roman era and the 15th-century Ottoman conquest. The Early Middle Ages in the Western Balkans saw the region reconquered from barbarians (Ostrogoths) by the Byzantine Emperor Justinian I, followed by raids and migrations carried out by Slavic peoples in the 6th and 7th centuries. The first mention of a distinct Bosnian region comes from the 10th-century Byzantine text De Administrando Imperio. By the late 9th and early 10th century, Latin priests had Christianized much of Bosnia, with some areas remaining unconverted. In the High Middle Ages, Bosnia experienced economic stability and peace under the Ban Kulin who ruled over Banate of Bosnia from 1180 to 1204 and strengthened its ties with the Republic of Ragusa and with Venice. The Kingdom of Bosnia emerged in the Late Middle Ages (1377). The kingdom faced internal and external conflicts, eventually falling under Ottoman rule in the late 15th and early 16th centuries.