In early historic times, Svealand was inhabited by the Svear (mentioned as the Suiones by Tacitus in the late 1st cent. A.D.). They engaged in wars with their southern neighbors, who inhabited Götaland and who according to an unproved tradition were the ancestors of the Goths. By the 6th cent. A.D. the Svear had conquered the Götar, with whom they merged. The early Swedes were combined and confused with other Scandinavians (e.g., the piratical Vikings and Norsemen). The Swedes alone, known as Varangians in Russia, extended (10th cent.) their influence to the Black Sea. The Swedish kings warred for centuries with their Danish and Norwegian neighbors.
St. Ansgar introduced Christianity c.829, but paganism was fully eradicated only in the 12th cent. by Eric IX, who also conquered Finland. The royal authority was weakened before the 13th cent. by the rise of an independent feudal class. The Swedish cities also began to acquire wide rights at that time and were strongly influenced by German merchants of the Hanseatic League, active especially at Visby. In 1319, Sweden and Norway were united under Magnus VII, and in 1397 Queen Margaret I effected the personal union of Sweden, Norway, and Denmark through the Kalmar Union.
However, Margaret's successors, whose rule was centered in Denmark, were unable to control the Swedes. Real power was held for long periods by regents (notably those of the Sture family) chosen by the Swedish diet. Christian II, who asserted his claim to Sweden by force of arms, ordered a massacre (1520) of Swedish nobles at Stockholm. This "Stockholm Blood Bath" stirred the Swedes to new resistance; at Strängnäs, in 1523, they made Gustavus Vasa their king as Gustavus I.
The founder of the modern Swedish state, Gustavus eliminated the influence of the Hanseatic League in Sweden, strengthened the central authority, made (1544) the kingship hereditary in the Vasa dynasty, and made Lutheranism the state religion. However, he was unable to regain the southern provinces, held by Denmark. His successor, Eric XIV (reigned 1560–68), began the Swedish conquest of Livonia by taking (1561) its northern section (Estonia).
Swedish interests in E Europe were further enhanced by the marriage of John III (reigned 1569–92), Eric's successor, to the sister of Sigismund II of Poland. Their son, Sigismund III of Poland, was a Roman Catholic; his accession (1592) to the Swedish throne was deeply resented by the Protestant Swedes. He was deposed in 1599, and his uncle became regent and then king of Sweden as Charles IX (reigned 1607–11).
Charles's son, Gustavus II (Gustavus Adolphus; reigned 1611–32), made Sweden a great European power. Through a war with Russia, he acquired (1617) Ingermanland and Karelia; from Poland he took nearly all of Livonia. By his victories at Breitenfeld (1631) and Lützen (1632) in the Thirty Years War, Gustavus made Sweden the dominant Protestant power of continental Europe. Axel Oxenstierna, appointed chancellor by Gustavus in 1612, was highly influential during Gustavus's reign and the first half of the reign of Queen Christina (1632–54).
In the 17th cent. Swedish colonial aspirations in North America (see New Sweden) proved short-lived. The Peace of Westphalia (1648; see Westphalia, Peace of), which ended the Thirty Years War, gave W Pomerania, Wismar, and the archbishopric of Bremen to Sweden, making the Swedish kings princes of the Holy Roman Empire. Charles X, who became king on the abdication (1654) of Christina, successfully led wars against Poland and Denmark. The southern provinces of Sweden were definitively recovered from Denmark in 1660. Under Charles XI (reigned 1660–97), Sweden became an absolute monarchy, and the great nobles lost their independence.
In the Northern War (1700–1721), which broke out shortly after the accession of Charles XII (reigned 1697–1718), Sweden was crushed after gaining its greatest military triumphs (e.g., at Narva and in Livonia). Under the treaties of Stockholm (1720) and Nystad (1721), Sweden ceded the archbishopric of Bremen to Hanover, part of Pomerania to Prussia, and Livonia, Ingermanland, and Karelia to Russia. Internally, Sweden was torn in the 18th cent. by political intrigue and civil discord. Ulrica Eleonora (d.1741) succeeded her brother, Charles XII, in 1718, but abdicated (1720) in favor of her husband, Frederick I (d. 1751), a prince of Hesse-Kassel.
The constitution of 1720 gave increased powers to the Riksdag (diet) and the political scene was dominated (1738–65) by the faction known as the Hats, who favored an aggressive anti-Russian policy in alliance with France and who represented the nobility and the bureaucracy. They were successfully challenged in 1765 by the Caps, who sought peaceful relations with Russia and who represented the lesser estates. In 1751 the house of Oldenburg-Holstein-Gottorp gained the Swedish throne when Adolphus Frederick became king. His son, Gustavus III (reigned 1771–92), restored absolutism in 1772 but was later assassinated by a conspiracy of nobles. Gustavus IV (reigned 1792–1809), a despotic ruler, involved Sweden in war with Napoleon I and then (1806–9) with Russia. A coup (1809) placed his uncle, Charles XIII, on the throne, and later in the same year Sweden was forced to cede Finland to Russia.
A constitutional monarchy was established by the constitution of 1809, which, although modified considerably (e.g., in 1866 and 1969), remained in effect until Jan. 1, 1975. From 1810, Swedish affairs were in the hands of Charles's adopted heir, Marshal Bernadotte (later Charles XIV). Sweden again joined the allies against Napoleon in 1813; this was the last war in which Sweden has participated. The Congress of Vienna compensated (1814) Sweden for its loss of Pomerania and Finland with Norway, which remained a separate kingdom in personal union with Sweden until 1905.
The history of 19th-century Sweden, under Charles XIV (reigned 1818–44), Oscar I (1844–59), Charles XV (1859–72), and Oscar II (1872–1907), was one of progressive liberalization in government and of industrial development. Freedom of the press (1844) and internal free trade (1864) were established, and the suffrage bill of 1865 enfranchised the middle class. The accelerated industrial development of the late 19th cent. was accompanied by the rise of the Social Democratic party, which dominated Swedish politics after 1920. From 1870 to 1914 about 1.5 million Swedes emigrated to the United States, mostly to the Midwest.
Relations with Norway were strained throughout the 19th cent., and in 1905 the union of Norway and Sweden was peacefully terminated. Under Gustavus V (reigned 1907–50), Sweden averted involvement in World War I and II, making armed neutrality the basis of its foreign policy, and, except for the early 1920s and early 1930s, enjoyed economic prosperity. Universal taxpayer suffrage was introduced in 1907, and in 1910 a workers' compensation insurance law began the long series of Swedish welfare legislation. Sweden entered the United Nations in 1946, and Dag Hammarskjöld, a Swedish diplomat, was secretary-general of the organization from 1953 until his death in 1961. In 1950, Gustavus VI ascended the throne; he was succeeded in 1973 by Charles XVI Gustavus. Sweden refused to join the North Atlantic Treaty Organization (NATO) in 1949 in order not to compromise its neutrality, and for similar reasons withdrew its first application for full membership in the European Community in 1971.
The Social Democrats, led by Tage Erlander from 1946 to 1969 and thereafter by Olof Palme, controlled the government after 1945, usually at the head of coalition governments. Considerable new social welfare legislation was passed, but from the mid-1960s Swedish economic growth slowed, and there were sizable increases in unemployment and in the rate of inflation in the early 1970s. Palme was replaced in 1976 by Thorbjörn Fälldin, a Center party member who led a coalition that ended 44 years of domination by the Social Democrats.
The period was marked by a heated national debate over nuclear power. Fälldin resigned in 1978 when he was forced to compromise on his decision to halt the building of nuclear power plants. Ola Ullsten became prime minister briefly, but Fälldin was returned to power after a general election in 1979. A 1980 referendum called for the phasing out of nuclear power, but in the subsequent decades most nuclear power plants remained in operation, and in 2010 legislation allowed for the issuing of permits for the construction of new nuclear power plants. In 1982 the Social Democrats resumed power under the leadership of Olof Palme, who was assassinated by an unidentified gunman in 1986. Palme was succeeded by Ingvar Carlsson. In 1991 the Social Democrats lost power and Carl Bildt, a Conservative, became prime minister; his government enacted austerity measures.
Carlsson and the Social Democrats were returned to power in the 1994 elections. Sweden joined the European Union in 1995. Carlsson resigned as prime minister in 1996 and was succeeded by his finance minister, Göran Persson, who continued in office following the 1998 elections, despite a setback for the Social Democrats. In 2002, Swedish voters again returned the Social Democrats to power, this time with an increased percentage of the vote. Sweden has deregulated many sectors of its economy while retaining its welfare state, and the country has experienced steady growth since the mid-1990s. A center-right coalition, led by the Moderate party, defeated the Social Democrats in Sept., 2006. Fredrik Reinfeldt, leader of the Moderates, became prime minister of a four-party coalition in October. In the Sept., 2010, elections the ruling coalition won the largest bloc of seats but fell short of a majority.