Johann Klaj (Latinized Clajus) (1616 – 16 February 1656) was a German poet.
He was born at Meissen in Saxony. After studying theology at University of Leipzig, Wittenberg,  he went to Nuremberg as a "candidate for holy orders," and there, in conjunction with Georg Philipp Harsdörffer, founded in 1644 the literary society known as the Pegnitz order. This references Julius Tittmann, Die Nürnberger Dichterschule (Göttingen, 1847).
In 1647 he received an appointment as master in the Sebaldus school in Nuremberg, and in 1650 became preacher at Kitzingen, where he died in 1656. Klaj's poems consist of dramas, written in stilted language and redundant with adventures, among which are Höllen- und Himmelfahrt Christi (Nuremberg, 1644), and Herodes, der Kindermörder (Nuremberg, 1645), and a poem, written jointly with Harsdörffer, Pegnesische Schäfergedicht (1644), which gives in allegorical form the story of his settlement in Nuremberg.
- Smither, Howard E. (1 September 2012). A History of the Oratorio: Vol. 2: the Oratorio in the Baroque Era: Protestant Germany and England. Chapel Hill: UNC Press Books. p. 72. ISBN 978-0-807-83776-4. Retrieved 24 February 2022.
- public domain: Chisholm, Hugh, ed. (1911). "Klaj, Johann". Encyclopædia Britannica. Vol. 15 (11th ed.). Cambridge University Press. p. 844. One or more of the preceding sentences incorporates text from a publication now in the
- Warrack, John (26 April 2001). German Opera: From the Beginnings to Wagner. Cambridge: Cambridge University Press. p. 21. ISBN 978-0-521-23532-7. Retrieved 24 February 2022.