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 watercolor 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'Accademia 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).