Livonian War in the context of "Union of Grodno (1566)"

Estonia under Swedish rule signifies the period of time between 1561 and 1710, when present-day Estonia was under the rule of the Swedish Empire. In the wake of the breakup of the State of the Teutonic Order, the Baltic German local nobility in the areas of Harrien (Harjumaa) and Wierland (Virumaa), as well as the city of Reval (Tallinn) in June 1561 (and somewhat later Jerwen (Järvamaa)) asked for and were granted protection by the Swedish king Eric XIV, leading to Swedish involvement in the Livonian War. At the conclusion of hostilities in 1583, Sweden was in control of the northern parts of modern Estonia and Dagö (Hiiumaa island); the Duchy of Estonia was created from this territory. Following renewed wars between Poland and Sweden, the southern parts of present-day Estonia (then Livonia) were incorporated into Sweden by the Treaty of Altmark in 1629. Sweden also conquered the island of Ösel (Saaremaa) from Denmark, and were thus in control of all of present-day Estonia.

The time of Swedish rule came to an effective end in 1710, when all the Swedish Baltic provinces capitulated to Russian troops during the end-stages of the Great Northern War. Russian hegemony was formalized in 1721.

The Kingdom of Livonia was a nominal state in what is now the territory of Estonia and Latvia. Russian tsar Ivan IV declared the establishment of the kingdom during the Livonian War of 1558–1583, but it never functioned properly as a polity.

The Duchy of Estonia (Swedish: Hertigdömet Estland; Estonian: Eestimaa hertsogkond; German: Herzogtum Estland), also known as Swedish Estonia (Swedish: Svenska Estland), was a dominion of the Swedish Empire from 1561 until 1721 during the time that most or all of Estonia was under Swedish rule. The territory was eventually ceded to Russia in the Treaty of Nystad, following its capitulation during a plague outbreak in the Great Northern War.

The dominion arose during the Livonian War, when the northern parts of present-day Estonia — Reval (Tallinn) and the counties of Harjumaa, Western Virumaa, Raplamaa and Järvamaa — submitted to the Swedish king in 1561, and Läänemaa in 1581. It is also colloquially known as the "good old Swedish times" (Estonian: vana hea Rootsi aeg) by Estonians, but this expression was not used before the following Russian rule, in the beginning of which the situation of Estonian peasantry declined rapidly; to gain the support of the German Baltic nobility, Russia gave them more power over the peasantry.

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.

The Treaty of Stettin (German: Frieden von Stettin, Swedish: Freden i Stettin, Danish: Freden i Stettin) of 13 December 1570, ended the Northern Seven Years' War fought between Sweden and Denmark with its internally fragmented alliance of Lübeck and Poland. It also settled Swedish, Danish, and Holy Roman Imperial claims regarding the Livonian War. Unfavourable for Sweden, the treaty assured Danish hegemony in Northern Europe for a short period. Yet, because of its inconclusiveness, it did not prevent further warfare between Denmark-Norway and Sweden, which ended only in the 1720s.