Oscar Fredrik von Sydow (12 July 1873 – 19 August 1936) was a Swedish politician who served briefly as Prime Minister of Sweden from 23 February to 13 October 1921.^[1]

Oscar von Sydow was the son of Henrik August von Sydow, a magistrate's clerk, and Euphrosyne Maria Modin. He was born in Kalmar and raised in Norrland. In 1890, he passed his higher education examination and proceeded to study Law at Uppsala University. In 1894, he graduated with a degree in the civil service.

In 1906, von Sydow was appointed Undersecretary of State at the Ministry for Civil Service Affairs, and in 1911 he became the Governor of Norrbotten County. In the governments of Hjalmar Hammarskjöld and Carl Swartz (1914–1917) he was Minister for Civil Service Affairs, during which time he established the Unemployment Commission (arbetslöshetskommissionen). Between 1917 and 1934, he was Governor of Gothenburg and Bohus County.

Following the sudden resignation of the Prime Minister Louis De Geer in 1921, the King had difficulties finding a candidate willing to form a new government, as the elections were drawing near. Hjalmar Branting declined, after being asked twice to become Prime Minister, and the appointment was offered to Oscar von Sydow, who accepted and took office on 23 February.

Von Sydow gave an ultimatum that he would not lead a powerless government and demanded that the Social Democratic Party promise to support him in important finance and defence issues. Despite such agreements, all of the propositions made by the new government were voted down by the opposition, and as a result von Sydow resigned on 13 October 1921. His lasting legacy as Prime Minister is for presenting the bill that abolished the death penalty in Sweden.

Von Sydow was Marshal of the Realm (riksmarskalk) from 1934 until his death in 1936.

• Sydow (surname)