In 1192 the Babenbergs’ territory was greatly extended when they won the duchy of Steiermark. In Steiermark the margraves of the family of the Otakars of Steyr had gradually asserted themselves—under conditions similar to those of the Babenbergs—over their rivals, the noble families of the Eppensteiner, Formbacher, and Aribonen. The most successful among Steiermark’s margraves was Otakar III (reigned 1130–63). Then, in 1180, Emperor Frederick I, in the course of a renewed anti-Welf policy, raised Steiermark to the status of a duchy and granted it complete independence from Bavaria. A few years later a treaty of inheritance (Georgenberg; 1186) was concluded between the dukes Leopold V of Austria (reigned 1177–94), a son of Henry II Jasomirgott, and Otakar IV of Steiermark, the ailing last Otakar ruler. When Otakar died in 1192, Leopold succeeded him, and thus the Babenbergs came into the inheritance.

Except for a short intermission (1194–98), the reigning Babenberg thereafter ruled both duchies, Austria and Steiermark. Steiermark then included parts of the Traungau, which eventually was to become part of Upper Austria, and the province of Pitten, north of the Semmering Alpine pass, afterward assigned to Lower Austria. In logical continuation of the Babenberg policy, Leopold VI (the Glorious) and his successor, Frederick II (the Warlike), the last representative of the dynasty, extended their domains farther south, gaining fiefs in Carniola.

Before he inherited the duchy of Steiermark, Leopold V had taken part in the Third Crusade, during which, on the ramparts of Acre (modern ʿAkko, Israel), he became involved in a quarrel with the English king Richard I (the Lion-Heart). Later, on his return journey to England, Richard tried to make his way through Austria in disguise but was recognized near Vienna, taken prisoner, and later handed over to the Holy Roman emperor Henry VI. England had to pay a heavy ransom, a share of which Leopold obtained and invested in the foundation, extension, and fortification of towns as well as in the stamping of a new coin, the so-called Wiener pfennig. The road connecting Vienna and Steiermark was improved, and the new town of Wiener Neustadt was established on its course to protect the newly opened route across the Semmering.

On Leopold V’s death the Babenberg domains were divided between his sons for four years, until the death of one of them, Frederick I, in 1198. His brother Leopold VI, the most outstanding member of the family, then took over as sole ruler (1198–1230). This was a time of great prosperity for the Babenberg countries. In imperial politics Leopold VI again took sides with the Hohenstaufen, backing Philip of Swabia. In church matters he was a great supporter of the monasteries, founding a Cistercian monastery at Lilienfeld (c. 1206). He tried to concentrate patronage rights over ecclesiastical property in his own hands and took rigorous action against the heretics (the Cathari and Waldenses). He participated in several crusades in Palestine, Egypt, southern France (against the Albigenses), and Spain (against the Saracens). Leopold VI’s efforts to emancipate Austria ecclesiastically by creating a separate Austrian bishopric in Vienna came to naught because of the opposition of the church in Passau and also in Salzburg; nor did his son Frederick II succeed in the same matter. Leopold VI played some role in imperial politics, bringing about the Treaty of San Germano between the Holy Roman emperor Frederick II and Pope Gregory IX (1230). He met his death in San Germano (now Cassino, Italy), and his body was transported to Lilienfeld for burial.

A change came about under the last representative of the dynasty, Frederick the Warlike, Leopold’s son. His harsh internal policy and military excursions against neighbouring lands, together with his opposition to the emperor Frederick II, led in 1237 to the temporary loss of both Austria and Steiermark. The crisis, however, was overcome, and fresh opportunities were about to open for the duke when, on June 15, 1246, he was killed in battle against the Hungarians on the Leitha River. With him the male line of the family came to an end.

The political history of Austria from the end of the 10th century to the middle of the 13th is marked by the establishment and consolidation of territories. This process was most advanced in the Babenberg domains but was not confined to them. Dukes Herman (1144–61) and Bernhard (1202–56) of Kärnten achieved a comparable status, and Count Albert of Tirol (died 1253) moved in the same direction. The archbishops of Salzburg strove to eliminate all secular powers and patrons of their see, but, in the other territories, secular princes strengthened their rule.

Another milestone of this period was the completion of the colonization of the Austrian territories. New settlements were established by clearing the woods and advancing to more remote mountain areas. Several old and new settlements grew into market centres and towns and were eventually granted charters. The colonization movement also affected the ratio of the German to non-German population. Except for some places in the Alpine regions, the Slavs were gradually assimilated, and the same held true of the remnants of the Roman population in Salzburg and northern Tirol.

The intellectual life of the period deserves mention. The Babenberg court was famous enough to attract some of the leading German poets. At the beginning of the 13th century, the saga known as the Nibelungenlied was written down by an unknown Austrian. Historical writing flourished in the monasteries. The era also produced first-rate Romanesque and early Gothic architecture.