Sweden's prehistory begins in the Allerød oscillation, a warm period around 12.000 BC, with Late Palaeolithic reindeer-hunting
camps of the Bromme culture at the edge of the ice in what is now the country's southernmost province, Scania. This period was
characterised by small clans of hunter-gatherers who relied on flint technology.
Shortly before the close of the Younger Dryas (c. 9.600 BC), the west coast of Sweden (Bohuslän) was visited by hunter-gatherers from
northern Germany. This cultural group is commonly referred to as the Ahrensburg culture and were engaged in fishing and sealing
along the coast of western Sweden during seasonal rounds from the Continent.
The Late Palaeolithic gave way to the first phase of the Mesolithic in c. 9.600 BC. This age, divided into the Maglemosian (9.000-6.000 BC),
Kongemosian (6.000–5.200 BC) and Ertebølle (5.300–3.950 BC) Periods, was characterised by small bands of hunter-gatherer-fishers
with a microlithic flint technology. Where flint was not readily available, quartz and slate were used.
Farming and animal husbandry, along with monumental burial, polished flint axes and decorated pottery, arrived from the Continent with the
Funnel-beaker Culture in c. 4.000 BC. The people of the country's northern two thirds retained an essentially Mesolithic lifestyle into
the first millennium BC.
Coastal south-eastern Sweden, likewise, reverted from neolithisation to a hunting and fishing economy after only a few centuries, with the
Pitted Ware Culture (3.500-2.300 BC). In 2.800 BC the Funnel Beaker Culture gave way to the Battle Axe Culture, a regional
version of the middle-European Corded Ware phenomenon.
Sweden's southern third was part of the stock-keeping and agricultural Nordic Bronze Age (1.750–500 BC) Culture's area. The Nordic
Bronze Age was entirely pre-urban, with people living in hamlets and on farmsteads with single-story wooden long-houses.
In the absence of any Roman occupation, Sweden's Iron Age is reckoned up to the introduction of stone architecture and monastic orders
about 1100 AD. Much of the period is proto-historical, that is, there are written sources but most hold a very low source-critical quality.
Until the 9th century, the Scandinavian people lived in small Germanic kingdoms and chiefdoms known as petty kingdoms. These
Scandinavian kingdoms and their royal rulers are mainly known from legends and scattered continental sources as well as from Runestones.
The Scandinavian people appeared as a group separate from other Germanic nations, and at this time there was a noticeable increase in
war expeditions (Viking raids) on foreign countries, which has given the name Viking Age (793–1066 AD) to this period. The Swedes
took part in many Western raids against England alongside the Danes and Norwegians of which many successfully acquired Danegeld
as seen on the England Runestones. The Swedes were also very active traders and raiders in the eastern and southeastern parts of Europe.
The large Russian mainland and its many navigable rivers offered good prospects for trading and plundering. These routes brought
them into contact with the Byzantine and Muslim empires.
In the 11th and 12th centuries, the sources state how Sweden more or less consisted of self-governing provinces. It is established that
Olof Skötkonung was king of Svealand and at least parts of Götaland, but it is uncertain whether his realm extended to include all
of it. And after Olof, the reign of the country was on several occasions divided between different rulers. King Sverker I of
Sweden (1134–1155) is said to have permanently integrated Götaland and Svealand. The following centuries saw rivalry between two houses:
the House of Sverker in the Östergötland province, and the House of Eric in the Västergötland province.
The greatest medieval statesman of Sweden, and one of the principal architects of its rise as a nation, Birger Jarl the Regent,
practically ruled the land from 1248 to 1266. He is today revered as the founder of Stockholm and as the creator of national legislation.
The First Swedish–Norwegian Union, was a personal union of the separate kingdoms of Sweden (which included large parts of nowadays
Finland) and Norway together with Norway’s overseas colonies (including Iceland, Greenland, the Faroe Islands and the northern isles of
Orkney and Shetlands). The union was founded by King Magnus Eriksson in 1319 and dissolved in 1355, briefly re-uniting in 1362 until
1365.
The Kalmar Union was a personal union in Scandinavia, agreed at Kalmar in Sweden, that from 1397 to 1523 joined under a single
monarch the three kingdoms of Denmark, Sweden (then including much of present-day Finland), and Norway. The union was the work of Scandinavian
aristocracy wishing to counter the influence of the Hanseatic League, a northern German trade league centered around the Baltic
and North Seas. More personally, it was achieved by Queen Margaret I of Denmark (1353–1412). She was a daughter of King Valdemar IV
and had married King Haakon VI of Norway and Sweden, who was the son of King Magnus IV of Sweden, Norway and Scania.
In the 16th century, Gustav Vasa (1490–1560) fought for an independent Sweden, crushing an attempt to restore the Union of Kalmar
and laying the foundation for modern Sweden. At the same time, he broke with the papacy and established the Lutheran Church in Sweden.
During the 16th and 17th centuries, the kings demanded ever increasing taxes and military conscription, emphasizing the need for defense.
However the money and manpower were used for offensive warfare. Indeed, when there seemed to be a real threat of invasion in 1655–1660,
King Charles X Gustav asked the people to give more and to manage their own defences. Finally a balance was reached that provided
a well supplied aggressive foreign policy. During the 17th century, after winning wars against Denmark, Russia, and Poland, Sweden
emerged as a great power by taking direct control of the Baltic region, which was Europe's main source of grain, iron, copper, timber,
tar, hemp, and furs.
Russia, Saxony–Poland, and Denmark–Norway pooled their power in 1700 and attacked the Swedish empire. Although the
young Swedish King Charles XII (1697–1718) won spectacular victories in the early years of the Great Northern War, most
notably in the stunning success against the Russians at the Battle of Narva (1700) where the Russian army was so severely devastated
that Sweden had an open chance to invade Russia. However, Charles XII did not pursue the Russian army, instead turning against Poland
and defeating the Polish king, Augustus II the Strong, and his Saxon allies at the Battle of Kliszów in 1702. This gave
Russia time to rebuild and modernise its army. After the success of invading Poland, Charles XII decided to make an attempt at invading
Russia, but this ended in a decisive Russian victory at the Battle of Poltava in 1709.
Returning to Sweden in 1715, Charles XII launched two campaigns against Norway on 1716 and 1718, respectively. During the second attempt,
he was shot to death during the Siege of Fredriksten Fortress. The Swedes were not militarily defeated at Fredriksten, but the
whole structure and organisation of the campaign fell apart with the king's death. Forced to cede large areas of land in the Treaty
of Nystad in 1721, Sweden also lost its place as an empire and as the dominant state on the Baltic Sea.
In interest of re-establishing Swedish dominance in the Baltic Sea, Sweden allied itself against its traditional ally and benefactor, France,
in the Napoleonic Wars. However, in 1810, a French Marshal, Jean-Baptiste Bernadotte, was chosen as heir presumptive to
Charles XIII; in 1818, he established the House of Bernadotte, taking the regnal name of Charles XIV.
Sweden's role in the Battle of Leipzig gave it the authority to force Denmark–Norway, an ally of France, to cede Norway to the
King of Sweden on 14 January 1814 in exchange for the northern German provinces, at the Treaty of Kiel. The Norwegian attempts
to keep their status as a sovereign state were rejected by the Swedish king, Charles XIII. He launched a military campaign against Norway
on 27 July 1814, ending in the Convention of Moss, which forced Norway into a personal union with Sweden under the Swedish crown,
which lasted until 1905.
Sweden was neutral in World War I, although the Swedish government was sympathetic to both sides at different times during the conflict,
even briefly occupying the Åland islands jointly with the Germans. At first, the Swedish government flirted with the possibility of changing
their neutral stance to side with the Central Powers, and made concessions to them including mining the Öresund straits to close them to
Allied warships wishing to enter the Baltic. Later the Swedish signed agreements allowing trade with the Allied powers and limiting trade
with Central Powers, though this brought about the fall of the government of Hjalmar Hammarskjöld.
Sweden followed a policy of armed neutrality during World War II, although thousands of Swedish volunteers fought in the Winter War
with Finland against the Soviets. Sweden did permit German troops to pass through its territory to and from occupation duties in Norway,
and supplied the Nazi regime with steel and ball-bearings.
Sweden was one of the first non-participants of World War II to join the United Nations (in 1946). Apart from this, the country tried
to stay out of alliances and remained officially neutral during the entire Cold War, never joining NATO.
During the Cold War Sweden maintained a dual approach, publicly the strict neutrality policy was forcefully maintained, but unofficially
strong ties were kept with the U.S., Norway, Denmark, West Germany, and other NATO countries. Swedes hoped that the U.S. would use conventional
and nuclear weapons in case of a Soviet attack on Sweden. A strong ability to defend against an amphibious invasion was maintained, complete
with Swedish-built warplanes, but there was no long-range bombing capability.
On 28 February 1986, the Social Democratic leader Prime Minister Olof Palme was assassinated. The murderer was never found. Shocked
Swedes worried whether the nation had lost its innocence.
In 1995, a few years after the end of the Cold War, Sweden became a member of the European Union and the old term "policy of neutrality"
fell out of use. In a referendum held in 2003, the majority voted not to adopt the Euro as the country's official currency.
Until recently Sweden remained non-aligned militarily, although it participated in some joint military exercises with NATO and some other countries.
However, in 2022, in response to the 2022 Russian invasion of Ukraine, Sweden moved to formally join the NATO alliance. On 10 July 2023,
after opposing the Swedish NATO application for 14 months, president Erdogan agreed to send the Swedish NATO application to the Turkish parliament
for ratification.