Eirik Mikael Hornborg (29 September 1879 – 29 December 1965) was a Finnish historian, educator, writer and politician, born in Helsinki.
During World War I, Hornborg was a prominent member of the secret network known as the Jäger movement, which was seeking to achieve Finnish independence with the support of the German Empire.
In the autumn of 1916, he participated in battles against the Imperial Russian Army on the Courland front.
After the February Revolution of 1917, he was able to return to Finland and to take up his duties as a Member of Parliament.
After the outbreak of the Finnish Civil War in January 1918, he went into hiding in Helsinki, which was controlled by the Red side, and worked as one of the most important organizers of the clandestine White movement in the city.