The Codex Borgia or Codex Yoalli Ehēcatl is a Mesoamerican ritual and divinatory manuscript. It is generally believed to have been written before the Spanish conquest of Mexico, somewhere within what is now southern or western Puebla. The Codex Borgia is a member of, and gives its name to, the Borgia Group of manuscripts. The Codex Borgia features eighteen pages of an astronomical narrative that shows the yearlong alteration of the rainy and dry season. The Codex Borgia is named after the Italian Cardinal Stefano Borgia, who owned it before it was acquired by the Vatican Library.