formerly (1624–1925) Christiania
City and municipality (pop., 2002 est.: municipality, 512,589), capital of Norway.
It lies at the northern end of Oslo Fjord and constitutes a separate county. It was founded by King Harald III Sigurdsson с 1050. Haakon V built the Akershus fortress с 1300. After it was destroyed by fire in 1624, King Christian II of Denmark-Norway built a new town farther west and called it Christiania. It grew in the 19th century, partly by absorbing neighbouring towns, and replaced Bergen as Norway's largest and most influential city. It was renamed Oslo in 1925 and developed rapidly after World War II. It is the country's principal commercial, industrial, and transportation centre, and its harbour is the largest and busiest in Norway.