Austrasia (old Ger. Oesterrych, i. e., Oestreich), the eastern kingdom of the Franks of the 6th, 7th, and 8th centuries, under the Merovingians, comprising in its flourishing period the countries on both sides of the Rhine, from the Marne to the Saale and from the North sea to the Danube (the ancient kingdoms or duchies of Metz, Champagne, Thuringia, Alemannia, Frisia, and others). The first king was Sieg-bert, to whom this territory fell in 561 on the partition of the dominions of his father Clo-taire I., king of the Franks. Australia was in conflict with Neustria, the western Frankish kingdom, and with the Burgundians. Among celebrated Austrasian rulers were Queen Brune-haut or Brunehilde (567-613), King Dagobert (628-'38), whose successors are called les rois faineants (idle kings), and the mayor of the palace Pepin of Heristal, who was succeeded in 714 by his natural son Charles Martel. In 752 Charles's son Pepin the Short became sovereign of both the eastern and western Frankish kingdoms, and Austrasia ceased to play a distinct part in history.

Under Charlemagne's successors most of the former Austrasian countries were merged into Germany, and those of Neus-tria into France. - See Histoire du royaume merovingien oVAustrasie, by Haguenin (Paris, 1863).