Duchy of Courland and Semigallia in the context of Anna of Russia

Subdivisions of the Polish–Lithuanian Commonwealth evolved over for centuries of its existence from the signing of the Union of Lublin to the third partition.

The lands that once belonged to the Commonwealth are now largely distributed among several central, eastern, and northern European countries: Poland (except western Poland), Lithuania, Latvia, Belarus, most of Ukraine, parts of Russia, southern half of Estonia, and smaller pieces in Slovakia and Moldova.

Livonia, known in earlier records as Livland, is a historical region on the eastern shores of the Baltic Sea. It is named after the Livonians, who lived on the shores of present-day Latvia.

By the end of the 13th century, the name was extended to most of present-day Estonia and Latvia, which the Livonian Brothers of the Sword had conquered during the Livonian Crusade (1193–1290). Medieval Livonia, or Terra Mariana, reached its greatest extent after the Saint George's Night Uprising (1343–1345), which forced Denmark to sell the Duchy of Estonia (northern Estonia conquered by Denmark in the 13th century) to the State of the Teutonic Order in 1346. Livonia, as understood after the retreat of Denmark in 1346, bordered on the Gulf of Finland in the north, Lake Peipus and Russia to the east, and Lithuania to the south.

Curonian colonisation is a collective name given to the colonisation efforts of the Duchy of Courland and Semigallia (today part of Latvia), a vassal duchy of the Polish–Lithuanian Commonwealth. Small, but wealthy, the Duchy took a modest part in the European colonization settlement attempts of West Africa and the Caribbean.

The Baltic Governorates, originally the Ostsee Governorates, was a collective name for the administrative units of the Russian Empire set up in the territories of Swedish Estonia, Swedish Livonia (1721) and, later, of the Duchy of Courland and Semigallia (1795).
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The Treaty of Vilnius was concluded on 28 November 1561, during the Livonian War, between the Livonian Confederation and the Grand Duchy of Lithuania in Vilnius. With the treaty, the non-Danish and non-Swedish part of Livonia, with the exception of the Free imperial city of Riga, subjected itself to the Grand Duke of Lithuania, Sigismund II Augustus with the Pacta subiectionis (Provisio ducalis). In turn, Sigismund granted protection from the Tsardom of Russia and confirmed the Livonian estates' traditional privileges, laid out in the Privilegium Sigismundi Augusti.

The secularization of the Livonian Order was the "final act" in Livonia's transition from the Middle Ages to the Early Modern era. The territories were re-organized in the Duchy of Courland and Semigallia and the Duchy of Livonia, the latter competing with the Kingdom of Livonia during the war. After its reconquest, Sigismund's successor Stephen Báthory ignored the privileges of 1561, granted a new constitution and initiated Counter-Reformation. These measures were reversed after the Swedish conquest. When after a further series of wars Livonia capitulated to Russia in 1710, the Privilegium Sigismundi Augusti was confirmed by Peter the Great.