Gustave-Achille Laviarde (November 17, 1841 – March 16, 1902) was, from 1882 to his death, pretender to the Kingdom of Araucanía and Patagonia under the name of "Achille I king of Araucanie".

Achille Laviarde was an active Bonapartiste, calling for the restoration of the French monarchy under the rule of a descendant of Napoleon Bonaparte.

He was implicated in the "Affaire du Comité Rémois" which was investigated by the French Parliament in 1875.

Previously, on August 28, 1873 the Criminal Court of Paris ruled that Antoine de Tounens, first king of Araucanía and Patagonia did not justify his status of sovereign.

[2] The pretenders to the throne of Araucanía and Patagonia are called monarchs and sovereigns of fantasy,[3][4][5][6][7] "having only fanciful claims to a kingdom without legal existence and having no international recognition".