The Duchy of Courland and Semigallia was a duchy in the Baltic region, then known as Livonia, that existed from 1561 to 1569 as a nominally vassal state of the Grand Duchy of Lithuania and subsequently made part of the Crown of the Polish Kingdom from 1569 to 1726 and incorporated into the Polish–Lithuanian Commonwealth in 1726. On 28 March 1795, it was annexed by the Russian Empire in the Third Partition of Poland.

Duchy of Courland and Semigallia - Wikipedia