Terra Mariana (Land of Mary) was the official name for Medieval Livonia or Old Livonia (German: Alt-Livland, Estonian: Vana-Liivimaa, Latvian: Livonija) which was formed in the aftermath of the Livonian Crusade in the territories comprising present day Estonia and Latvia. It was established on February 2, 1207, as a principality of the Holy Roman Empire but lost this status in 1215 when proclaimed by Pope Innocent III as a direct subject to the Holy See.
Terra Mariana was divided into feudal principalities by Papal Legate William of Modena:
- Duchy of Estonia (Dominum directum to the King of Denmark)
- Archbishopric of Riga
- Bishopric of Courland
- Bishopric of Dorpat
- Bishopric of Ösel-Wiek
- Military administration of the Livonian Brothers of the Sword
After the 1236 Battle of Saule the surviving members of the brothers merged in 1237 with the Teutonic Order of Prussia and became known as the Livonian Order. In 1346 the order bought Danish Estonia. Throughout the existence of medieval Livonia there was a constant struggle over the supremacy of ruling the lands by the Church, the Order, the secular German nobility and the citizens of the Hanseatic towns of Riga and Reval. Following its defeat in the Battle of Grunwald in 1410 the Teutonic Order and the Ordenstaat fell into decline but the Livonian Order managed to maintain its independent existence. In 1561, during the Livonian war, Terra Mariana ceased to exist. Its northern parts were ceded to Sweden and formed into the Duchy of Estonia, its southern territories became part of the Grand Duchy of Lithuania — and thus eventually of the Polish–Lithuanian Commonwealth as the Duchy of Livonia and Duchy of Courland and Semigallia. The island of Saaremaa became part of Denmark.
Since beginning of the 20th century Terra Mariana (Estonian: Maarjamaa) has been used as a poetic name or sobriquet for Estonia. In 1995 The Order of the Cross of Terra Mariana state decoration was instituted to honor the independence of the Estonia.