Denmark is a Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark, also known as the Danish Realm, a constitutionally unitary state that includes the autonomous territories of the Faroe Islands and Greenland in the north Atlantic Ocean. Metropolitan Denmark, also called "continental Denmark" or "Denmark proper", consists of the northern Jutland peninsula and an archipelago of 406 islands. It is the southernmost of the Scandinavian countries, lying southwest of Sweden, south of Norway, and north of Germany, with which it shares a short border. Denmark proper is situated between the North Sea to the west and the Baltic Sea to the east.

The Kingdom of Denmark, including the Faroe Islands and Greenland, has roughly 1,400 islands greater than 100 square metres (1,100 sq ft) in area; 443 have been named and 78 are inhabited. Denmark's population is over 6 million (1 May 2025), of which roughly 40% live in Zealand, (Sjælland) the largest and most populated island in Denmark proper; Copenhagen, (København) the capital and largest city of the Danish Realm, is situated on Zealand and Amager and Slotsholmen. Composed mostly of flat, arable land, Denmark is characterised by sandy coasts, low elevation, and a temperate climate. Denmark exercises hegemonic influence in the Danish Realm, devolving powers to the other constituent entities to handle their internal affairs. Home rule was established in the Faroe Islands in 1948; Greenland achieved home rule in 1979 and further autonomy in 2009.

The unified Kingdom of Denmark emerged in the eighth century AD as a maritime power amid the struggle for control of the Baltic Sea. In 1397, it formed the Kalmar Union with Norway and Sweden. This union persisted until Sweden's secession in 1523. The remaining Kingdom of Denmark–Norway endured a series of wars in the 17th century that resulted in further territorial cessions. A surge of nationalist movements in the 19th century were defeated in the First Schleswig War of 1848. The adoption of the Constitution of Denmark on 5 June 1849 ended the absolute monarchy. In the Second Schleswig War Denmark lost Schleswig-Holstein, which led to changes in Danish politics henceforth emphasising social cohesion in the diminished realm, as well as the clearing of the vast moors of Jutland for agriculture, new Christian movements split between Indre Mission and Grundtvig, but generally a stronger self-perception among the people of belonging to a unified country and state. In 1920 North Schleswig became Danish.

Denmark began industrialising in the mid 19th century, becoming a major agricultural exporter. It introduced social and labour market reforms in the early 20th century, forming the basis for the present welfare state model and advanced mixed economy. Denmark remained neutral during World War I; Danish neutrality was violated in World War II by a rapid German invasion in April 1940. During occupation, a resistance movement emerged in 1943, while Iceland declared independence in 1944; Denmark was liberated after the end of the war in May 1945. In 1973, Denmark, together with Greenland but not the Faroe Islands, became a member of what is now the European Union; however, it negotiated certain opt-outs, such as retaining its own currency, the krone.

Denmark is a developed country with an advanced high-income economy, high standard of living, and robust social welfare policies. Danish culture and society are broadly progressive egalitarian, and socially liberal; Denmark was the first country to legally recognise same-sex partnerships. It is a founding member of NATO, the Nordic Council, the OECD, the OSCE, the Council of Europe and the United Nations, and is part of the Schengen Area. Denmark maintains close political, cultural, and linguistic ties with its Scandinavian neighbours. The Danish political system, which emphasizes broad consensus, is used by American political scientist Francis Fukuyama as a reference point for near-perfect governance; his phrase "getting to Denmark" refers to the country's status as a global model for stable social and political institutions.

The etymology of the name "Denmark", the relationship between "Danes" and "Denmark", and the emergence of Denmark as a unified kingdom are topics of continuous scholarly debate. This is centred primarily on the morpheme "Dan" and whether it refers to the Dani or a historical person Dan and the exact meaning of the -"mark" ending.

Most etymological dictionaries and handbooks derive "Dan" from a word meaning "flat land", related to German Tenne "threshing floor", English den "cave". The element mark is believed to mean woodland or borderland (see marches), with probable references to the border forests in south Schleswig.

The first recorded use of the word Danmark within Denmark itself is found on the two Jelling stones, which are runestones believed to have been erected by Gorm the Old, considered to be Demark's first king, (c. 955) and Harald Bluetooth (c. 965). The larger of the two stones is popularly cited as the "baptismal certificate" (dåbsattest) of Denmark, though both use the word "Denmark", in the accusative ᛏᛅᚾᛘᛅᚢᚱᚴ tanmaurk ([danmɒrk]) on the large stone, and the genitive ᛏᛅᚾᛘᛅᚱᚴᛅᚱ "tanmarkar" (pronounced [danmarkaɽ]) on the small stone, while the dative form tąnmarku (pronounced [danmarkʊ]) is found on the contemporaneous Skivum stone. The inhabitants of Denmark are there called tani ([danɪ]), or "Danes", in the accusative.