Gustav Johann Ludvik Tönnies (January 16, 1814 – November 12, 1886) was a Swedish and Austro-Hungarian carpenter, architect and industrialist, who lived most of his life in Ljubljana.

[1] During the period of the great social and economic change in Europe, Gustav Tönnies and his nine sons were among some of the most famous and respected industrialists, architects and builders of Ljubljana (from 1845 to 1936).

Because the completed work was to an exceptionally high standard, Ljubljana Major Johann Nepomuk Hradeczky offered Gustav Tönnies the position of city carpenter.

[2] In 1895, an earthquake struck Ljubljana and the Tönnies Company was a great asset to the rebuilding of the city supplying the much needed construction materials for the building projects in progress.

The machinery developed included that what was used in forestry industry; wood processing; pumps and turbines; belt presses and the instruments for measuring earthquakes.