The Jäger March Op. 91a (Finnish: Jääkärimarssi, originally Jääkärien marssi) was composed by Jean Sibelius in 1917 to the words written by the Finnish Jäger, Hilfsgruppenführer Heikki Nurmio who served in Libau, in the Royal Prussian 27th Jäger Battalion of the Imperial German Army. This unit was fighting against the Russian Empire, of which the Grand Duchy of Finland still was a part. The words were smuggled into Finland to Sibelius, who composed the song in Järvenpää.
The Jäger March, a military march, was originally written for male chorus and piano, and Sibelius later arranged it for male chorus and symphony orchestra.
The first public performance of Jäger March was in Helsinki January 19, 1918 by Akademiska sångföreningen, led by Olof Wallin. The Finnish Civil War began on the same day between the White and the Red troops. The march is the honorary march of many army detachments.