Sweden, formally the Kingdom of Sweden, is a Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At 450,295 square kilometres (173,860 sq mi), Sweden is the largest Nordic country by both area and population, and is the fifth-largest country in Europe. Its capital and largest city is Stockholm. Sweden has a population of 10.6 million, and a low population density of 25.5 inhabitants per square kilometre (66/sq mi); 88% of Swedes reside in urban areas. They are mostly in the central and southern half of the country. Sweden's urban areas together cover 1.5% of its land area. Sweden has a diverse climate owing to the length of the country, which ranges from 55°N to 69°N.

Sweden has been inhabited since prehistoric times around 12,000 BC. The inhabitants emerged as the Geats (Swedish: Götar) and Swedes (Svear), who formed part of the sea-faring peoples known as the Norsemen. A unified Swedish state was established during the late 10th century. In 1397, Sweden joined Norway and Denmark to form the Scandinavian Kalmar Union, which Sweden left in 1523. When Sweden became involved in the Thirty Years' War on the Protestant side, an expansion of its territories began, forming the Swedish Empire, which remained one of the great powers of Europe until the early 18th century. During this era Sweden controlled much of the Baltic Sea. Most of the conquered territories outside the Scandinavian Peninsula were lost during the 18th and 19th centuries. The eastern half of Sweden, present-day Finland, was lost to Imperial Russia in 1809. The last war in which Sweden was directly involved was in 1814, when Sweden by military means forced Norway into a personal union, a union which lasted until 1905.

Sweden is a highly developed country ranked fifth in the Human Development Index. It is a constitutional monarchy and a parliamentary democracy, with legislative power vested in the 349-member unicameral Riksdag. It is a unitary state, divided into 21 counties and 290 municipalities. Sweden maintains a Nordic social welfare system that provides universal health care and tertiary education for its citizens. It has the world's 14th highest GDP per capita and ranks very highly in quality of life, health, education, protection of civil liberties, economic competitiveness, income equality, gender equality and prosperity. Sweden joined the European Union on 1 January 1995 and NATO on 7 March 2024. It is also a member of the United Nations, the Schengen Area, the Council of Europe, the Nordic Council, the World Trade Organization and the Organisation for Economic Co-operation and Development (OECD).

The name for Sweden is generally agreed to derive from the Proto-Indo-European root *s(w)e, meaning 'one's own', referring to one's own tribe from the tribal period. The native Swedish name, Sverige (a compound of the words Svea and rike, first recorded in the cognate Swēorice in Beowulf), translates as "realm of the Swedes", which excluded the Geats in Götaland.

The contemporary English variation was derived in the 17th century from Middle Dutch and Middle Low German. As early as 1287, references are found in Middle Dutch referring to a lande van sweden ("land of [the] Swedes"), with swede as the singular form. In Old English the country was known as Swéoland or Swíoríce, and in Early Modern English as Swedeland. Some Finnic languages, such as Finnish and Estonian, use the terms Ruotsi and Rootsi; these variations refer to the Rus' people who inhabited the coastal areas of Roslagen in Uppland and who gave their name to Russia.

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.

Sweden and its people were first described by the Roman historian Publius Cornelius Tacitus in his Germania (98 AD). In Germania 44 and 45 he mentions the Swedes (Suiones) as a powerful tribe with ships that had a prow at each end (longships). Which kings (*kuningaz) ruled these Suiones is unknown, but Norse mythology presents a long line of legendary and semi-legendary kings going back to the last centuries BC. The runic script was in use among the south Scandinavian elite by at least the second century AD, but all that has survived from the Roman Period is curt inscriptions demonstrating that the people of south Scandinavia spoke Proto-Norse at the time, a language ancestral to Swedish and other North Germanic languages.

In the sixth century, the Byzantine historian Jordanes names two tribes living in Scandza, both of which are now considered to be synonymous with the Swedes: the Suetidi and Suehans. The Suehans were known to the Roman world as suppliers of black fox skins and, according to Jordanes, had very fine horses, similar to those of the Thyringi of Germania ("alia vero gens ibi moratur Suehans, quae velud Thyringi equis utuntur eximiis").