Joseph Kaspar Mertz (in Hungarian: Mertz János Gáspár) (17 August 1806 – 14 October 1856) was an Austro-Hungarian guitarist and composer.Caspar Joseph Mertz (baptised Casparus Josephus Mertz) was born in Pressburg, now Bratislava (Slovakia), then the capital of the Kingdom of Hungary and part of the Austrian Empire. He never used his full name when performing or on his publications, preferring only the initials "J. K.". The name "Johann Kaspar" first appeared in the German guitar journal "Der Guitarrefreund" in 1901 and since that time has been incorrectly repeated. In 1900 J. M. Miller used the name "Joseph K. Mertz" for his publication of three previously unpublished manuscripts of Mertz in Three Compositions For Guitar.