Clavis Artis is the title of an alchemical manuscript published in Germany in three volumes in the late 17th or early 18th century, attributed to Zoroaster (Zarathustra). It features numerous watercolour illustrations depicting alchemical images, as well as pen drawings of laboratory instruments.

Three copies of the manuscript are known to exist, one at the Biblioteca dell???ccademia Nazionale dei Lincei in Rome, one at the Biblioteca Civica Attilio Hortis in Trieste, and one at the Bayerische Staatsbibliothek in Munich. There is no information about the author and the origin of the manuscript, but there are references to a Rosicrucian order (Orden der Gold- und Rosenkreutzer).