The Finnish 27th Jäger Battalion (German: Königlich Preussisches Jägerbataillon Nr. 27) was an elite light infantry unit in the German Army from 1915–1918 which consisted mainly of volunteers of the Finnish Jäger troops.
The recruitment of the Jäger volunteers from the Russian Grand Duchy of Finland had to be secret, and was dominated by German-influenced circles, such as university students and the upper middle class. The recruitment was however in no way exclusive. The recruits were transported across Finland's western border via Sweden to Germany, where the volunteers were formed into the Royal Prussian 27th Jäger Battalion. It was a continuation and expansion of the "Boy Scout Training" (Pfadfinderkursus).
Later, the Pfadfinderkursus received more permanent forms and the course was changed into a permanent training group in Lockstedt, the Ausbildungs-Truppe-Lockstedt, which had given military training to Finnish volunteers eager to fight for independence.
More than 200 university students had participated in the so-called Boy Scout training – they dressed in Boy Scout uniforms during training, and they became the officers of the Finnish Jäger Troops. This group was expanded by extensive recruitment in the autumn of 1915 and spring of 1916. The goal was to increase the unit to 1,200 men, including artillery and pioneers. As the new recruits included working class young men and farmers as well as sailors, not so many of them knew German. It was therefore necessary to create military guide books in Finnish, and a command vocabulary was created.
On 9 May 1916, the Lockstedt training group (Ausbildungs-Truppe-Lockstedt) was designated the Royal Prussian Jaeger Battalion number 27 (Königlich Preussisches Jägerbataillon Nr. 27) and received new, green German Jaeger uniforms. Some of the soldiers to be trained stayed in Ausbildungs-Truppe-Lockstedt and their unit preserved its name. If the number of the recruits had increased enough, Ausbildungs-Truppe-Lockstedt would itself have been formed in due course as a Jaeger battalion, but with the number 28 (i.e. German: Königlich Preussisches Jägerbataillon Nr. 28). This did not happen as there was no political initiative for this in Finland or in Germany, which were preparing for a separate peace with the Russian Empire in order to fight more effectively on the Western Front against France and the United Kingdom.