Stephen Tvrtko II (; died in November 1443), also known as Tvrtko Tvrtković (), was a member of the House of Kotromanić who reigned as King of Bosnia from 1404 to 1409 and again from 1420 to his death. Tvrtko II was the son of King Tvrtko I. His reigns took place during a very turbulent part of Bosnian history. He was first installed as a puppet king by the kingdom's leading noblemen, Hrvoje Vukčić Hrvatinić and Sandalj Hranić Kosača, to replace his increasingly independent uncle Ostoja. Five years later, he lost the support of the nobility and thus the crown as well. He was hardly politically active during the second reign of Ostoja, but managed to depose and succeed Ostoja's son Stephen. Tvrtko's second reign was marked by repeated Turkish raids, which forced him to accept the Ottoman suzerainty, and the struggle for power with Radivoj, another son of Ostoja. Tvrtko was married twice, but died childless. He was succeeded by his chosen heir, Radivoj's brother Thomas. Background Tvrtko II was the son of Tvrtko I, the first King of Bosnia. The identity of his mother, and thus the legitimacy of his birth, is disputed. The uncertainty also stems from the complex religious situation in medieval Bosnia, where it was often hard to discern between legitimate and illegitimate offspring. The 16th-century Ragusan historian Mavro Orbini, writing of Tuartco Scuro (Tvrtko the Plain), claimed that he was born to Tvrtko I's concubine, a Bosnian noblewoman named Vukosava, and this view was taken for granted by subsequent writers. In the 19th century, Vjekoslav Klaić argued that Tvrtko II's mother was his father's wife, Dorothea of Bulgaria. Klaić cited as evidence Tvrtko I's charter of 1382, in which the King mentioned Queen Dorothea and an unnamed son to the government of the Republic of Ragusa. If Tvrtko II is the son his father mentioned in this charter, his birth would have had to have taken place between 1375 (Tvrtko I and Dorothea having married in December 1374) and the date the charter was issued. King Tvrtko I died unexpectedly in March 1391, shortly after Queen Dorothea. The Council of the Kingdom, composed of the country's most prominent noblemen, elected his elderly relative, Dabiša, as his successor, rather than the deceased King's son, who was too young at the time. Upon Dabiša's death in 1395, the noblemen elected his widow, Helen. Three years