The Octofone is a stringed instrument that belongs to the mandola family. It is classified as a composite chordopone according to the Hornbostel-Sachs system. Due to its small amount of popularity it is often mistaken for an eight string guitar. Its strings are tuned in courses which is common to the instruments in the mandola family. It got it's name from the advertisement claim by the company Regal that it was eight instruments in one during the late 1920's and early 1930's.
It is most commonly tuned, from thickest to thinnest string, to G-d-a-e'. According to the scientific designation this would be written as G2-D3-A3-E4.