Frederick II (German: Friedrich II.), known as Frederick the Quarrelsome (Friedrich der Streitbare), was Duke of Austria and Styria from 1230 until his death. He was the fifth and last Austrian duke from the House of Babenberg, since the former margraviate was elevated to a duchy by the 1156 Privilegium Minus. He was killed in the Battle of the Leitha River, leaving no male heirs.
Born in Wiener Neustadt, Frederick was the second surviving son of the Babenberg duke Leopold VI of Austria and Theodora Angelina, a Byzantine princess. The death of his elder brother Henry in 1228 made him the only heir to the Austrian and Styrian duchies. Frederick succeeded his father in 1230. Proud of his Byzantine descent, the young duke soon was known as the Quarrelsome because of his harsh rule and frequent wars against his neighbors, primarily with Hungary, Bavaria and Bohemia. Even the Austrian Kuenring ministeriales, which had so far been faithful to the ruling house, started an insurgency as soon as his reign began.
Duke Frederick's ambitious plans were dashed when he died at the Battle of the Leitha River, in a border conflict he had picked with the Hungarian king Béla IV. He is buried at Heiligenkreuz Abbey.
As the last Babenberg duke, Frederick the Quarrelsome signifies the end of an era in the history of Austria, beginning with the enfeoffment of Margrave Leopold I in 976.