Amadis de Gaula (original Old Spanish and Galician-Portuguese spelling) (Spanish: Amadís de Gaula, IPA: [amaˈðiz ðe ˈɣaula]; Portuguese: Amadis de Gaula, IPA: [ɐmɐˈðiʒ ðɨ ˈɣawlɐ]; "Amadis of Gaul") is a landmark work among the knight-errantry tales which were in vogue in 16th century Iberian Peninsula, and formed the earliest reading of many Renaissance and Baroque writers, although it was written at the onset of the 14th century.

The first known printed edition was published in Zaragoza in 1508, by Garci Rodríguez de Montalvo (or Garci Ordóñez de Montalvo). It was published in four books in Castilian, but its origins are unclear: The narrative originates in the late post-Arthurian genre and had certainly been read as early as the 14th century by the chancellor Pero López de Ayala as well as his contemporary Pero Ferrús.

Montalvo himself confesses to have amended the first three volumes, and to be the author of the fourth. Additionally, in the Portuguese Chronicle by Gomes Eannes de Azurara (1454), Amadis is attributed to Vasco de Lobeira, who was knighted after the battle of Aljubarrota (1385). However, other sources claim that the work was, in fact, a copy of one João de Lobeira, not the Basque troubadour Vasco de Lobeira, and that it was a translation into Castilian Spanish of an earlier work, probably from the beginning of the 14th century, although no privimitive version in the original Portuguese is known. The inspiration for the "Amadis de Gaula" appears to be the blocked marriage of Infanta Constanza of Aragon with Henry of Castile in 1260 (See Juan Manuel's Libro de las Armas of 1335), as blocked was also Oriana's marriage to Amadis. A more recent, minority opinion attributes "Amadis" to Henry of Castile and León, due to evidence linking his biography with the events in "Amadis". Henry of Castile died in 1305.