Harria (Est. Harjumaa) was a province of medieval Livonia, corresponding to the northeastern coast of modern Estonia, conquered in the course of the Baltic Crusades in the thirteenth century. Harria was originally a central province south of the coastal land called Revalia, but during the thirteenth century the name came to be applied to both areas. The name of Revalia survived only in the name of the city and castle of Reval (mod. Tallinn, Estonia).
The chronicle of Henry of Livonia mentions important Estonian hill forts at Lone (mod. Lohu), Warbola (mod. Var- bola), and Keava; Raigele (mod. Raikküla) was known as a meeting place of the surrounding Estonian tribes. The German crusaders based in Riga began to mount raids into Harria in 1216, but after the Danes gained control of Reval in 1219, Harria was disputed between the two Christian powers until the Treaty of Stensby awarded the province to the king of Denmark (1238). Harria was the region with the greatest development of new manors, and the royal vassals in Harria and Vironia emerged as a powerful corporation able to pursue its own interests and policies. The rapid development of a manorial system has been regarded as a main reason for the St. George’s Night revolt of the native Estonians, which started in Harria in 1343.
In 1346 Harria was sold together with the rest of North Estonia to the Teutonic Order. Reval became the center of administration. The order extended the inheritance rights of the nobility of Harria and Vironia in 1397 to secure their support for the policies of the order in Livonia, but it was also to develop its own domains in Harria.