Amadís de Gaula (often referred to in English as Amadis of Gaul) is a work of fiction on the subject of knight-errantry. Its origins are disputed, though its likely area of origin is Portugal and it was probably written in the 14th Century. However, the earliest extant version is in Castilian and was published in the 16th century.

Amadís was son of a King and a princess. Abandoned at birth by his mother, he grew up as knight in a different kingdom. After many hardships, he meets his father, who was unaware of his existence, and marries a princess. He was corteous, gentle, sensitive and a devout christian. Contrary to most literary heroes of his time (French and German, for example) Amadis was a handsome man who would cry if refused by his lady, but invincible in battle, usually drenched in his own and his opponent´s blood.

Called also Amadis sin Tiempo (Amadis without Time) by his mother (in allusion to the fact that being conceived outside marriage she would have to abandon him and he would probably die), he is the most representative hero of the Cavalier novel genre. His adventures ran for three books, probably the most popular of their time.

The books show a complete idealization and simplification of knight-errantry. Even servants are hardly heard of, but there are many princesses, ladies and kings. Knights and damsels in distress are found everywhere. The book's style is reasonably modern, but lacks dialogue and the character´s impressions, mostly describing the action.

Noteworthy characters include Urganda la desconocida (Urganda the unknown), an ambiguous priestess with magical powers allowing her to change her aspect at will (hence the name) and the Endriago, a winged abomination born from two ogres, living in an island until Amadís manages to kill it.

As mentioned above, the origin of Amadís and his adventures is disputed. A Spanish writer, Garci Rodríguez de Montalvo, edited and published the first printed edition (and earliest extant version) in three volumes in 1508. While the third volume is generally regarded as Rodríguez de Montalvo's own work, he claimed to be publishing earlier sources and it is generally accepted that the first two volumes derive from a previous manuscript or oral tradition.

A Portuguese origin is most widely accepted but Amadis has also been claimed by the Spanish, French and Italians. Also, the action seems, from the names of characters and places, to be supposed to be set in England — Gaula, for instance, seems to be a distortion of Wales.

In any case, Rodríguez de Montalvo's Spanish version is considered the definitive one, and it was the one who made the character widely known. In the decades following its publication, several sequels of steadily declining quality (and fairly clearly not regarded as set in England) were published in Spanish and other languages, together with a number of other imitative works — and Miguel de Cervantes wrote Don Quixote as a parody of the resulting genre. Cervantes and his protagonist Quixote, however, hold the original Amadis in very high esteem.