Ernst Ruben Lagus (12 October 1896, Koski Hl – 15 July 1959, Lohja) was a Finnish Major General. Lagus was one of the Finnish Jaeger troops trained in the volunteer Royal Prussian 27th Jäger Battalion. During the Winter War he was in charge of the supplies of the troops fighting in Karelian Isthmus. In the Continuation War he was first the commander of (Jaeger Brigade) and later Panssaridivisioona (Armoured Division). He was the first soldier to be awarded the Mannerheim Cross on 22 July 1941.