Frederick II, known as the Quarrelsome (1219–June 15, 1246), from the dynasty of Babenberg, was the duke of Austria and Styria from 1230 to 1246.

He was the only son of Duke Leopold VI and Theodora Angela , a Byzantine princess. His first spouse was another Byzantine named Laskaris , and his second wife was Agnes of Meran. He had no sons, and the male line of the Babenberg dynasty ended with him.

Frederick was known as the Quarrelsome because of his frequent wars against his neighbors, primarily with Hungary, Bavaria and Bohemia. Even the Kuenringer family, which had so far been faithful to the ruling house, started an insurgency as soon as his reign began. But most dangerous were his disputes with Emperor Frederick II, who ostracized him in 1236. During the years of his ban, Vienna became a imperial free city for some years. However, he managed to maintain his position in Wiener Neustadt. In 1239, in a spectacular change in imperial politics, Frederick became one of the emperor's most important allies. Negotiations about the elevation of Vienna to a bishopric and of Austria (including Styria) to a kingdom were initiated. However, the duke's niece Gertrud would have had to marry the almost fifty-year-old emperor, which the girl refused.

Duke Frederick finally died in a battle against the Hungarian king Béla IV by the Leitha river.

As the last Babenberg duke, Frederick the Quarrelsome signifies the end of an era in the history of Austria. With his overambitious plans, which were frequently foiled by his erratic character, he somewhat resembled his later successor Rudolf IV. As the Privilegium Minus also allowed women to inherit, his sister Margaret and his niece Gertrude of Austria would have been entitled to the throne. Gertrude first married Herman VI, Margrave of Baden, who did not manage to maintain his position in Austria, and later Roman of Halicz , a relative of the king of Hungary. Margaret was married to Premysl Ottokar II of Bohemia, more than twenty years her junior. Subsequently, Austria became of field of conflict between the Premysl and Arpad dynasties, in which Ottokar would prevail until being overthrown by Rudolph of Habsburg.