Mestre João Faras, better known simply as Mestre João ('Master John"), was an astrologer, astronomer, physician and surgeon of King Manuel I of Portugal who accompanied Pedro Álvares Cabral in the discovery of Brazil in 1500, and wrote a famous letter identifying the Southern Cross constellation.
The celebrated 1500 letter of Mestre João Faras was discovered in the Portuguese royal archives by the historian Francisco Adolfo de Varnhagen, and published for the first time in 1843.
Despite much search, the figure of Mestre João Faras remains elusive. In his 1500 letter, Mestre João identifies himself simply as a bacherel of arts and medicine ('bachelor' was a general term for someone with formal learning) and a personal physician and surgeon of the King Manuel I of Portugal.
Besides the 1500 letter, the only other concrete clue we have of Mestre João's existence is an (unpublished) manuscript translation of Pomponius Mela's De Situ Orbis from Latin into imperfect Castilian. He may also have gone by the name 'Johannes Emeneslau'.
On account of his poor command of Portuguese and penchant for Spanish (Castilian), Mestre João Faras is generally believed to have been originally of the existing nationalities in what would be Spain later (whether Castilian, Galician or Aragonese has been alternatively proposed). He was almost certainly a Sephardi Jew. He probably fled Spain for Portugal after the 1492 Alhambra decrees, but ended up converting after 1496, to enter the service of King Manuel I of Portugal.