Vilhelm Aleksander Thesleff (July 27, 1880 in Vyborg - March 26, 1941 in Helsinki) was a Finnish general, first Minister of defence of Finland and briefly the commander in chief of the Finnish army.
Thesleff began a military career in 1894 Hamina Cadet School from which he graduated in 1901. He continued his military studies in St Petersburg, Nikolai General Staff Academy in the years 1904-1907, and the Officers Cavalry School 1910-1911. He was promoted to the rank of lieutenant-colonel, 12 June 1912.
Thesleff attended the first world war the Russian army in 1914-1917, until he was taken by the German's as a prisoner of war in Riga in September 1917. In October 1917 he was transferred due to a request by the military committee to serve as a liaison officer between the Finnish Jäger battalion fighting under the German command and the Germans. He deposed the unpopular Colonel Nikolai Mexmontan. He was the commander of the Finnish Jäger battalion 27 from 6 November 1917 until 25 February 1918. In March 1918 he was appointed as a liaison officer with the German Baltic Division during the Finnish Civil War.
After the Finnish Civil War Thesleff became the War Minister, 27 May 1918 - 27 November 1918 in the first cabinet of Juho Kusti Paasikivi. He was promoted to the rank of Major General, 14 June 1918. After the resignation of Major General Wilkman, as a war minister, Thesleff became commander in chief of the Finnish military forces chief in 13 August 1918.
Paasikivi cabinet had been leaning towards the Imperial Germany. When Germany was defeated in the First World War the cabinet resigned. This also ment the end of Thesleff's political career.