The Duchy of Courland and Semigallia (Latin: Ducatus Curlandi et Semigalli; German: Herzogtum Kurland und Semgallen; Latvian: Kurzemes un Zemgales hercogiste; Lithuanian: Kuro ir iemgalos kunigaiktyst; Polish: Ksistwo Kurlandii i Semigalii) 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 PolishLithuanian Commonwealth in 1726. On 28 March 1795, it was annexed by the Russian Empire in the Third Partition of Poland.

There was also a short-lived wartime state existing from 8 March to 22 September 1918 with the same name. Plans for it to become part of the United Baltic Duchy, subject to the German Empire, were thwarted by Germany's surrender of the Baltic region at the end of the First World War. The area became a part of Latvia at the end of World War I.

The Partitions of Poland were three partitions of the Polish–Lithuanian Commonwealth that took place toward the end of the 18th century and ended the existence of the state, resulting in the elimination of sovereign Poland and Lithuania for 123 years. The partitions were conducted by the Habsburg Monarchy, the Kingdom of Prussia, and the Russian Empire, which divided up the Commonwealth lands among themselves progressively in the process of territorial seizures and annexations.The First Partition was decided on August 5, 1772 after the Bar Confederation lost the war with Russia. The second partition occurred in the aftermath of the Polish–Russian War of 1792 and the Targowica Confederation of 1792 when Russian and Prussian troops entered the Commonwealth and the Second Partition was signed on January 23, 1793 (Austria did not participate in the Second Partition). The Third Partition took place on October 24, 1795, in reaction to the unsuccessful Polish Kościuszko Uprising the previous year. With this partition, the Commonwealth ceased to exist.In English, the term "Partitions of Poland" is sometimes used geographically as toponymy, to mean the three parts that the partitioning powers divided the Commonwealth into, namely: the Austrian Partition, the Prussian Partition and the Russian Partition. In Polish, there are two separate words for the two meanings. The consecutive acts of dividing and annexation of Poland are referred to as rozbiór (plural: rozbiory), while the term zabór (pl. zabory) means each part of the Commonwealth annexed in 1772–95 becoming part of Imperial Russia, Prussia, or Austria. Following the Congress of Vienna in 1815, the borders of the three partitioned sectors were redrawn; the Austrians established Galicia in the Austrian partition, whereas the Russians gained Warsaw from Prussia and formed an autonomous polity of Congress Poland in the Russian partition.

In Polish historiography, the term "Fourth Partition of Poland" has also been used, in reference to any subsequent annexation of Polish lands by foreign invaders. Depending on source and historical period, this could mean the events of 1815, or 1832 and 1846, or 1939. The term "Fourth Partition" in a temporal sense can also mean the diaspora communities that played an important political role in re-establishing the Polish sovereign state after 1918.