The last Babenberg duke died without sons in 1246, his widowed sister of about 47 married a 19-year-old Ottokar and handed him her title deeds, and he divorced her

Duke Frederick II of Austria, the last Babenberg duke, was killed in battle at the Leitha on 15 June 1246 and left no heir. His sister Margarete, born about 1204, was the widow of Henry (VII), King of the Romans. Henry had been captured in 1235 and died in Italy in 1242 after a fall from his horse; the Neue Deutsche Biographie notes it may have been suicide. Margarete returned to Austria to claim her inheritance. On 11 February 1252 at Hainburg she married Ottokar, the 19-year-old Přemyslid heir of Bohemia. At the wedding she handed him the charters to her lordship in Austria. A plan to end the marriage was first mentioned in 1256. In 1261 Ottokar separated from her on the grounds that she was childless and had taken religious vows; the pope approved on 20 April 1262. She left Prague on 18 October 1261, and about a week later Ottokar married Kunigunde of Chernigov. Margarete died at Krumau am Kamp on 29 October 1266 and was buried at Lilienfeld abbey. Ottokar kept Austria and refused to swear allegiance to the new king, Rudolf of Habsburg. He gave up Austria in 1276, went back to war, and was captured and killed on the Marchfeld on 26 August 1278. In 1282 Rudolf granted Austria to his sons, the start of Habsburg rule there.