Johann Kaspar Mertz (August 17, 1806 - October 14, 1856) was a Hungarian guitarist and composer. János Gáspár Mertz was born in Pozsony, Hungary. He was active in Vienna (c.1840~1856), which had been home to various prominent figures of the guitar, including Anton Diabelli, Mauro Giuliani, Wenceslaus Matiegka and Simon Franz Molitor. A virtuoso, he established a solid reputation as a performer. He toured Moravia, Poland, and Russia, and gave performances in Berlin and Dresden. In 1846 Mertz nearly died of an overdose of strychnine that had been prescribed to him as a treatment for neuralgia.