The octobass is an extremely large and rare bowed string instrument first built around 1850 in Paris by the French luthier Jean-Baptiste Vuillaume (1798–1875).

It has three strings and is essentially a larger version of the double bass – the specimen in the collection of the Musée de la Musique in Paris measures 3.48 metres (11 ft 5 in) in length, whereas a full-size double bass is generally approximately 2 m (6 ft 7 in) in length.

Because of the extreme fingerboard length and string thickness, the musician plays it using a system of levers and pedals.

[1] The only known work from the 19th century that specifically calls for the octobass is Charles Gounod's Messe solennelle de Sainte-Cécile.

The instrument is a copy of those made by Vuillaume, but with innovative elements, especially in the mechanics, and of which a library of samples from Daniele Bertinelli and Giorgio Riolo was created in collaboration with SoundIron.

[7] The second octobass is owned by Guro Moe, an experimental musician who commissioned the instrument to the German luthier Wolfgang Staab.