The Treaty of Vilnius or Vilna was concluded on 31 August 1559, during the Livonian War

Livonian War

The Livonian War was fought for control of Old Livonia in the territory of present-day Estonia and Latvia when the Tsardom of Russia faced a varying coalition of Denmark–Norway, the Kingdom of Sweden, the Union of the Grand Duchy of Lithuania and the Kingdom of Poland.During the period 1558–1578,...

, between the Livonian Order

Livonian Order

The Livonian Order was an autonomous Livonian branch of the Teutonic Order and a member of the Livonian Confederation from 1435–1561. After being defeated by Samogitians in the 1236 Battle of Schaulen , the remnants of the Livonian Brothers of the Sword were incorporated into the Teutonic Knights...

 and the Polish-Lithuanian Commonwealth

Polish-Lithuanian Commonwealth

The Polish–Lithuanian Commonwealth was a dualistic state of Poland and Lithuania ruled by a common monarch. It was the largest and one of the most populous countries of 16th- and 17th‑century Europe with some and a multi-ethnic population of 11 million at its peak in the early 17th century...

 at Vilnius

Vilnius

Vilnius is the capital of Lithuania, and its largest city, with a population of 560,190 as of 2010. It is the seat of the Vilnius city municipality and of the Vilnius district municipality. It is also the capital of Vilnius County...

 (Vilna, Wilna, Wilno). Gotthard von Kettler put the lands of the order under protection of Polish king and Grand Duke of Lithuania, Sigismund II Augustus

Sigismund II Augustus

Sigismund II Augustus I was King of Poland and Grand Duke of Lithuania, the only son of Sigismund I the Old, whom Sigismund II succeeded in 1548...

. The alliance was intended to neutralize the imminent threat of annexation of the order's lands by Russia

Russia

Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...

, yet despite earning military support from Polish-Lithuanian chancellor Mikołaj "the Black" Radziwiłł, Kettler was unable to prevent the occupation of most of Livonia by Russian forces. Thus, Kettler concluded a second treaty

Treaty of Vilnius (1561)

The Treaty of Vilnius or Vilna was concluded on 28 November 1561, during the Livonian War, between the Livonian Confederation and the Polish-Lithuanian Commonwealth at Vilnius...

 with Poland-Lithuania on 28 November 1561, transferring the remnants of the Teutonic Order State to the Polish Crown and the Grand Duchy of Lithuania

Grand Duchy of Lithuania

The Grand Duchy of Lithuania was a European state from the 12th /13th century until 1569 and then as a constituent part of Polish-Lithuanian Commonwealth until 1791 when Constitution of May 3, 1791 abolished it in favor of unitary state. It was founded by the Lithuanians, one of the polytheistic...

, himself becoming a vassal of Sigismund II Augustus.