Trondheim, formerly called Nidaros and Trondhjem (Southern Sami: Tråante), is an urban municipality in Trøndelag, and the third most populous municipality in Norway (after Oslo and Bergen) with 205,163 inhabitants as of 1 January 2020, after the merger with Klæbu municipality. The city center (Midtbyen) is located between Nidelva and Trondheimsfjorden. The municipality borders in the east towards Malvik, in the south towards Selbu and Melhus, and towards Indre Fosen in Trondheimsfjorden. The city is the headquarters for the county mayor, but not the county municipality or the county governor's office, as these functions are located in Steinkjer.

According to Olav Tryggvason's saga, the city was established by Olav Tryggvason in the year 997, and the city celebrated its millennium anniversary in 1997.

Trondheim is a center for higher education, and houses the largest campus at the country's largest university. In 1767, the Science Museum was established. The Norwegian University of Science and Technology (NTH) was established in 1910. The Norwegian University of Science and Technology (NTNU) was established in 1996.

St. Olav's hospital was established on Øya in Trondheim in 1910, under the name Nye Trondhjem hospital. It is today one of Norway's largest health trusts and is owned by Helse Midt-Norge. Cultural institutions are also represented in the cityscape. Trondheim Art Museum was established in 1997 and Rockheim was opened in 2010.

Trondheim is a hub for the railway in Norway; here the Dovre line meets from the south with the Meråker line and the Nordlands line north. Europavei 6 runs through the municipality. The city's airport is Trondheim Airport, Værnes in Stjørdal municipality.



It is believed that the city was founded in the year 997 by Olav Tryggvason. Archaeological finds indicate that there were also settlements around the Nidelva outlet even before that time beyond farms, probably sea arches for trading activities. Tomb finds have been made that confirm settlement on Nidarneset in the center of today's city center around 400 BC.

Nidaros Cathedral was built between 1070 and 1300, and is Norway's most central church. The constitution of 1814 stated that it was to be the coronation church for Norway's regent; this no longer applies, but since 1958 it has been used for signing by the royals. According to tradition, Nidaros Cathedral is the tomb of Olav the Holy; however, later excavations in Trondheim have revealed Clemenskirken, where the saint's coffin was placed on the altar in the year 1031, the year after the battle of Stiklestad. The diocese of Nidaros was established between 1070 and 1080; around 1152 it was elevated to a Catholic archdiocese that existed until the Reformation in 1537. Between 1434 and 1537, the archbishops of Nidaros minted their own coins.

The Ladejarls had their base in Nidaros from the end of the ninth century until 1029. Several of the medieval kings also resided here. A city fire in 1681 was one of the triggering reasons for the construction of Kristiansten fortress; this fortress gained importance during the great nordic war 1700–1721. The municipality received its current extent on 1 January 1964 when Trondheim was merged with the four neighboring municipalities Byneset, Strinda, Tiller and Leinstrand. As a result of the latest municipal reform, Klæbu will be incorporated in Trondheim on 1 January 2020.

By the end of the 11th century, the city grew very rapidly. Among other things, a stone church was built at St. Olav's cemetery, where Nidaros Cathedral is located today. A bridge was also built over the river approximately where the current Elgeseter bridge is located. In 1219, Trondheim experienced the first known city fire, and a few years later, in 1295, large parts of the city were reduced to ashes by another fire.

When the archbishopric of Nidaros was established in 1152, the city grew further, and from the 13th century, almost twenty churches are known under the seat. A number of monasteries were also built in the city, including Elgeseter, Bakke farm and Munkholmen.

From the 17th century, increased trade activity benefited the city. The city began to grow to the west, and the first settlements on Bakklandet emerged. In 1681, the so-called Hornemans fire left large parts of Trondheim in rubble, which led to Christian V deciding that a completely new city plan should be laid for Trondheim to prevent future fires from creating equal damage. The task was given to the Luxembourg Major General Johan Caspar de Cicignon, who promoted a city plan with wide and straight streets with a central square.

Despite this, several large fires broke out during the 18th and 19th centuries. A law was passed on the construction of masonry on the city center, but before this was passed, the city was quickly rebuilt with wooden buildings. Many of today's wooden buildings in the city center date from the middle of the 19th century.

After World War II, large parts of the old buildings had to give way in favor of new business activities. Cicignon's city plan from the end of the 17th century is nevertheless quite prominent in today's Trondheim.