This is the first ever thematic-bibliographic inventory of the composers compositions. It summarises and combines information from a number of reference works from recent years, most importantly the complete critical edition of Nielsens works (Carl Nielsen Udgaven, 19982009). It includes incipits (that is, the first couple of bars) for unambiguous identification of each piece or movement, in addition to information on different versions, the date of composition, first performance, and a survey of manuscript and printed sources from Nielsens lifetime. The printed edition of the Catalogue of Carl Nielsens Works is an abridged version of the online catalogue published by the Danish Centre for Music Editing at the Royal Library in Copenhagen.