Sofus Anton Birger Arctander (22 January 1845 - 20 August 1924) was a politician with the Liberal Party who served as acting Prime Minister of Norway during 1905.^[1]

Sofus Arctander was born in Christiania (now Oslo), Norway. He was the son of Hans Steenbuch Arctander (1801-1885) and Martha Dahll Nielsen (1804-1896). When he was eight years old, his family moved to Kristiansand in Vest-Agder. He was a teacher and librarian in Selje and Nordfjordeid. He received a law degree from the University of Christiania in 1870, then studied economy and philosophy at the University of Lund in 1871.

Arctander lived at Hadsel in Nordland (1872-1884). He was deputy judge and then acting district stipendiary magistrate before establishing himself as a lawyer in 1875. In 1880 he became bailiff in Hadsel.^[2]

In 1877, Arctander was elected deputy Member of the Parliament of Norway for the County of Nordland. From 1880 to 1884 he was a permanent member. He participated actively in the founding of the Liberal Party in 1882. Arctander was re-elected to Parliament for the period 1889-1891 and 1900-1906. He subsequently become mayor of Kristiania 1908-1920.

He was Minister of the Interior 1884–1885, Norwegian state secretary in Stockholm 1885–1886, Minister of the Interior 1886-1888, Norwegian Minister of Trade 1905–1907, acting Prime Minister 1905 and Minister of Trade 1907–1908 and 1910. ^[3]

In 1887, he was promoted to Commander with Star (Commander 1st Class) of the Order of St. Olav. Arctander also was appointed a Grand Cross of the Order of Dannebrog (Denmark) and a Commander Grand Cross of the Order of the Polar Star (Sweden). He was an honorary member and co-founder of the Nordlendingenes Forening, an association of people who have emigrated from the counties in Northern Norway. In 1912 he was awarded the Petter Dass Medal (Petter Dass-medaljen). Arctander died in the Lifjell Mountains of Telemark one day in August 1924, the exact date uncertain. He had been missing for some days when he was found dead.^[4]

He was married in 1881 with Maren Sophie Aars (1849-1940), daughter of Jens Ludvig Aars (1808-1855) and Annette Lund (1818-1855). They were the parents of Signy Arctander.^[5][6]