Oslo is the capital and largest city of Norway. It constitutes both a county and a municipality. The municipality of Oslo had a population of 724,290 in 2025, while the city's greater urban area had a population of 1,110,887 in 2025, and the metropolitan area had an estimated population of 1,546,706 in 2021.
During the Viking Age, the area was part of Viken. Oslo was founded as a city at the end of the Viking Age in 1040 under the name Ánslo, and established as a kaupstad or trading place in 1048 by Harald Hardrada. The city was elevated to a bishopric in 1070 and a capital under Haakon V of Norway around the year 1300. Personal unions with Denmark from 1397 to 1523 and again from 1536 to 1814 reduced its influence. After being destroyed by a fire in 1624, during the reign of King Christian IV, a new city was built closer to Akershus Fortress and named Christiania in honour of the king. It became a municipality (formannskapsdistrikt) on 1 January 1838. The city functioned as the capital of Norway during the 1814–1905 union between Sweden and Norway. From 1877, the city's name was spelled Kristiania in government usage, a spelling that was adopted by the municipal authorities in 1897, although 'Christiania' was also used. In 1925, the city, after incorporating the village retaining its former name, was renamed 'Oslo'. In 1948, Oslo merged with Aker, a municipality which surrounded the capital and which was 27 times larger, thus creating the modern, much larger Oslo municipality.
Oslo is Norway's primate city, being its dominant economic and governmental centre, and its metropolitan area is approximately 3.5 times more populated than the country's second-largest urban area, containing the second-largest city, Bergen. The city is also a hub of Norwegian trade, banking, industry and shipping. It is an important centre for maritime industries and maritime trade in Europe. The city is home to many companies within the maritime sector, some of which are among the world's largest shipping companies, shipbrokers and maritime insurance brokers. Oslo is a pilot city of the Council of Europe and the European Commission intercultural cities programme.
Oslo is considered a global city and was ranked as a "Beta World City" by the Globalization and World Cities Research Network in 2008. It was ranked number one in terms of quality of life among European large cities in the European Cities of the Future 2012 report by fDi magazine. A survey conducted by ECA International in 2011 placed Oslo as the second most expensive city in the world for living expenses after Tokyo. In 2013, Oslo tied with the Australian city of Melbourne as the fourth most expensive city in the world, according to the Economist Intelligence Unit's Worldwide Cost of Living study.
Oslo's population was increasing at record rates during the early 2000s, making it the fastest growing major city in Europe at the time. This growth originates primarily from international immigration and related high birth rates, but also from intra-national migration. By 2010 the immigrant population in the city was growing somewhat faster than the Norwegian population, and in the city proper this had become more than 25% of the total population if the children of immigrant parents were included.
Urban region
The municipality of Oslo has a population of 724,290 as of 1 January 2025. The urban area extends far beyond the boundaries of the municipality into the surrounding county of Akershus (municipalities of Asker, Bærum, Lillestrøm, Enebakk, Rælingen, Lørenskog, Nittedal, Gjerdrum, Nordre Follo); being, to a great degree suburbs of Oslo making up approximately 500,000 of the population of the greater Oslo region. The total population of this agglomeration was 1,546,706 in 2023. The city centre is situated at the end of the Oslofjord, from which point the city sprawls out in three distinct "corridors"—inland north-eastwards, and southwards along both sides of the fjord—which gives the urbanized area a shape reminiscent of an upside-down reclining "Y" (on maps, satellite pictures, or from high above the city).
To the north and east, wide forested hills (Marka) rise above the city giving the location the shape of a giant amphitheatre. The urban municipality (bykommune) of Oslo and county (fylke) of Oslo are two parts of the same entity, making Oslo the only city in Norway where two administrative levels are integrated. Of Oslo's total area, 130 km2 (50 sq mi) is built-up and 9.6 km2 (3.7 sq mi) is agricultural. The open areas within the built-up zone amount to 22 km2 (8.5 sq mi).
The city of Oslo was established as a municipality on 3 January 1838 (see formannskapsdistrikt). It was separated from the county of Akershus to become a county of its own in 1842. The rural municipality of Aker was merged with Oslo on 1 January 1948 (and simultaneously transferred from Akershus county to Oslo county). Furthermore, Oslo shares several important functions with Akershus county.
In addition is Marka (1,610 residents, 301.1 km2), that is administered by several boroughs; and Sentrum (1,471 residents, 1.8 km2) that is partially administered by St. Hanshaugen, and in part directly by the city council. As of 27 February 2020, there were 2,386 residents who were not allocated to a borough.
The nine municipalities directly included in the Urban area of Oslo.
Name and seal
After being destroyed by a fire in 1624, during the reign of King Christian IV, a new city was built closer to Akershus Fortress and named Christiania in the king's honour. The old site east of the Aker river was not abandoned, however, and the village of Oslo remained as a suburb outside the city gates. The suburb called Oslo was eventually included in the city proper. In 1925 the name of the suburb was transferred to the whole city, while the suburb was renamed "Gamlebyen", literally "the Old town", to avoid confusion.
The Old Town is an area within the administrative district Gamle Oslo. The previous names are reflected in street names like Oslo gate (Oslo street)
and Oslo hospital.
Toponymy
The origin of the name Oslo has been the subject of much debate. It is almost certainly derived from Old Norse and was—in all probability—originally the name of a large farm at Bjørvika, while the meaning of that name is disputed. Modern linguists generally interpret the original Óslo, Áslo or Ánslo as either "meadow at the foot of a hill" or "meadow consecrated to the Gods", with both considered equally likely.
Erroneously, it was once assumed that Oslo meant "the mouth of the Lo river", a supposed previous name for the river Alna. Not only has no evidence been found of a river "Lo" predating the work where Peder Claussøn Friis first proposed this etymology, but the very name is ungrammatical in Norwegian: the correct form would have been Loaros (cf. Nidaros). The name Lo is now believed to be a back-formation arrived at by Friis in support of his [idea about] etymology for Oslo.
Seal
Oslo is one of very few cities in Norway, besides Bergen and Tønsberg, that does not have a formal coat of arms, but which uses a city seal instead. The seal of Oslo shows the city's patron saint, St. Hallvard, with his attributes, the millstone and arrows, with a naked woman at his feet. He is seated on a throne with lion decorations, which at the time was also commonly used by the Norwegian kings.
Other names
Oslo has various nicknames and names in other languages. The city is sometimes known as "The Tiger City" (Norwegian: Tigerstaden), probably inspired by an 1870 poem by Bjørnstjerne Bjørnson which referenced then-Christiania in central Oslo. The nickname is mostly used by Norwegians from out of town, and rarely by people from the Oslo region.
History
Viking Age
During the Viking Age, the area that includes modern Oslo was located in Viken, the northernmost province of Denmark. Control over the area shifted between Danish and Norwegian kings in the Middle Ages, and Denmark continued to claim the area until 1241.
According to the Norse sagas, Oslo was founded around 1049 by Harald Hardrada. Recent archaeological research, however, uncovered Christian burials which could be dated to prior to AD 1000, evidence of a preceding urban settlement. This called for the celebration of Oslo's millennium in 2000 rather than 2049.
1000–1600
Under the reign of Olaf III of Norway (1067–1093), Oslo became a cultural centre for Eastern Norway. Hallvard Vebjørnsson became the city's patron saint and is depicted on the city's seal.
In 1174, Hovedøya Abbey was built. The churches and abbeys became major owners of large tracts of land, which proved important for the city's economic development, especially before the Black Death.
At the end of the 12th century, Hanseatic League traders from Rostock moved into the city and gained major influence in the city.
On 25 July 1197, Sverre of Norway and his soldiers attacked Oslo from Hovedøya.
During the Middle Ages, Oslo reached new heights during the reign of Haakon V of Norway (1299–1319). He was the first king to reside permanently in the city, and it has been regarded as the capital city of Norway since his reign. He also started the construction of the Akershus Fortress and the Oslo Kongsgård.
The Black Death came to Norway in 1349 and, like other cities in Europe, the city suffered greatly. The churches' earnings from their land dropped so much that the Hanseatic traders dominated the city's foreign trade in the 15th century.
In 1380, Norway was the weaker part in a personal union with Denmark, and Oslo's role was reduced to that of provincial administrative centre, with the monarchs residing in Copenhagen.
17th century
Over the years, fires destroyed significant parts of the city multiple times, as many of the city's buildings were built entirely of wood. After the fourteenth calamity, in 1624, which lasted for three days, Christian IV of Denmark decided that the old city should not be rebuilt again. His men built a network of roads on the other side of the bay in Akershagen near Akershus Castle. He demanded that all citizens move their shops and workplaces to the newly built city of "Christiania", named in his honour. The part of the city built starting in 1624 is now often called Kvadraturen because of its orthogonal layout in regular, square blocks. Anatomigården is a historic timber framing house located on the north side of Christiania Torv; it was built in 1640.
The transformation of Christiania went slowly for the first hundred years. However, outside of the city at Vaterland, Grønland, and the old town of Oslo, a new, unmanaged part of the city arose populated by citizens of lower class status.
The last Black Death outbreak in Oslo occurred in 1654.
18th century
In the 18th century, after the Great Northern War, the city's economy boomed with shipbuilding and trade. The strong economy transformed Christiania into a trading port.
19th century
The Royal Frederick University (now the University of Oslo) was founded in 1811; the fact that it was founded this late reportedly had an adverse effect on the development of the nation.
In 1814 the former provincial town of Christiania became the capital of the independent Kingdom of Norway, when the union with Denmark was dissolved and replaced by a personal union with Sweden. Several state institutions were established and the city's role as a capital initiated a period of rapidly increasing population. The government of this new state needed buildings for its expanding administration and institutions. Several important buildings and landmarks were erected in the 19th century, including the Royal Palace (1825–1848), the Stock Exchange (1826–1828), the Bank of Norway (1828), the Storting (1861–1866), the National Theatre (1899), and several University buildings. Among the world-famous artists who lived here during this period were Henrik Ibsen and Knut Hamsun (the latter was awarded the Nobel Prize for literature).
Large areas of the surrounding Aker municipality were incorporated in 1839, 1859, and 1878. The 1859 expansion included Grünerløkka, Grønland, and Oslo. At that time the area called Oslo (now Gamlebyen or Old Town) was a village or suburb outside the city borders east of Aker river. The population increased from approximately 10.000 in 1814 to 230.000 in 1900. In 1850, Christiania overtook Bergen and became the most populous city in the country. Christiania expanded its industry from 1840, most importantly around Akerselva. There was a spectacular building boom during the last decades of the 19th century, with many new apartment buildings and renewal of the city centre, but the boom collapsed in 1899.
In 1877 the city was renamed Kristiania.
20th century
The city and municipality used the name Kristiania until 1 January 1925 when the original name of Oslo was restored. This was because Norway became fully independent in 1905, and Norwegians argued that a name memorializing a Danish king (Christian IV of Denmark) was inappropriate as the name of the capital of their country.
The municipality developed new areas such as Ullevål garden city (1918–1926) and Torshov (1917–1925). City Hall was constructed in the former slum area of Vika from 1931 to 1950. In 1948, Oslo merged with Aker, a municipality which surrounded the capital and was 27 times larger, thus creating the modern, vastly enlarged Oslo municipality. At the time, Aker was a mostly affluent, green suburban community, and the merger was unpopular in Aker. Other suburbs, such as Lambertseter, began to be developed in the 1950s. Aker Brygge was constructed on the site of the former shipyard, Akers Mekaniske Verksted, from 1982 to 1998.
Norway was invaded by Germany on 9 April 1940. Efforts to stop the invasion, most notably the sinking of the Blücher, delayed the occupation of Oslo for several hours which allowed King Haakon VII to escape the city. Oslo remained occupied throughout the war until Germany capitulated in 1945. During this time, the occupying troops were harried by saboteurs in acts of resistance. On 31 December 1944, allied bombers missed their intended target and hit a tram, resulting in 79 civilian deaths.
21st century
During the 2011 Norway attacks, Oslo was hit by a bomb blast that ripped through the Government Quarter, damaging several buildings including the building that houses the Office of the Prime Minister. Eight people died in the bomb attack.
On 25 June 2022, two people were killed and 21 others injured in a mass shooting. An Iranian-born Norwegian citizen was subsequently charged with "aggravated terrorism".
The city has continued to expand. For a few years, new large scale housing areas and infrastructure projects are being built and planned across the city, notably in Hasle, Helsfyr, Bjørvika, Nydalen and Sinsen, this is increasing the density in and around Ring 2 and Ring 3. The Fornebu line on the metro is under construction as of 2024, and further subway lines crossing the inner city are being planned.