Arnaut Daniel (Occitan: [a?'nawd dani'?l]; fl. 1180-1200) was an Occitan troubadour of the 12th century, praised by Dante as "the best smith" (miglior fabbro) and called a "grand master of love" (gran maestro d'amore) by Petrarch. In the 20th century he was lauded by Ezra Pound in The Spirit of Romance (1910) as the greatest poet to have ever lived.
According to one biography, Daniel was born of a noble family at the castle of Ribérac in Périgord; however, the scant contemporary sources point to him being a jester with pernicious economic troubles. It is probable that he became friends with another troubadour named Bertran de Born as the de Born addresses an "Arnaut the joglar" in the tornada of one of his poems while Arnaut addresses a "Betran" in one of his own. The two likely met in the court of Richard Coeur de Lion which Daniel frequented. With the previously mentioned court, Daniel traveled to Paris, Spain, and perhaps Italy; in Paris Daniel attended the coronation of Philip Augustus.  Raimon de Durfort calls him "a student, ruined by dice and shut-the-box".
The dominant characteristic of Daniel's poetry is an extreme obscurity of thought and expression, a style called trobar clus ('hermetic verse'). He belonged to one school of troubadour poets that sought to make their meanings difficult to understand through the use of unfamiliar words and expressions, enigmatical allusions, complicated meters and uncommon rhyme schemes. Daniel further invented a form of stanza in which no lines rhymed with each other, finding their rhymes only in the corresponding line of the next stanza.
Daniel was the inventor of the sestina, a song of six stanzas of six lines each, with the same end words repeated in every stanza, though arranged in a different and intricate order. Henry Wadsworth Longfellow claims he was also the author of the metrical romance of Lancillotto, or Launcelot of the Lake, but this claim is completely unsubstantiated; Dante's reference to Daniel as the author of prose di romanzi ("proses of romance") remains, therefore, a mystery. There are sixteen extant lyrics of Arnaut Daniel only one of which can be accurately dated, to 1181. Of the sixteen there is music for at least one of them, but it was composed at least a century after the poet's death by an anonymous author. No original melody has survived.
Daniel's attempt to avoid simple and commonplace expressions in favor of striving for newer and more subtle effects found an admirer in Dante who would imitate the sestina's form in more than one song. Petrarch also wrote several sestinas as the form later gained popularity with Italian poets.
It is not believed that it is a coincidence that Dante wrote about Daniel in eight lines, as that was the favored amount of lines per stanza that the troubadours preferred to write. Dante also replicated that style and stanza length in six out of the eleven Occitan poems that Dante references in his De Vulgari Eloquentia.
Throughout the entirety of the Divine Comedy, Dante upholds the ideas of Italian superiority extending from the Roman Empire into that of "modern" language. This is displayed in his writing of Arnaut Daniel in Occitan thus, in one commentator's opinion, mocking the closed and difficult style of troubadour poetry (trobar clus), compared to the open sweetness of Italian poetry.
In homage to these lines which Dante gave to Daniel, the European edition of T. S. Eliot's second volume of poetry was titled Ara Vos Prec. In addition, Eliot's poem The Waste Land opens and closes with references to Dante and Daniel. The Waste Land is dedicated to Pound as "il miglior fabbro" which is what Dante had called Daniel. The poem also contains a reference to Canto XXVI in its line "Poi s'ascose nel foco che gli affina" ("Then he hid in the fire that purifies them") which appears in Eliot's closing section of The Waste Land as it does to end Dante's canto.
Arnaut's 4th canto contains the lines that Pound claimed were "the three lines by which Daniel is most commonly known" (The Spirit of Romance, p. 36):