A thematic catalogue is an index used to identify musical compositions through the citation of either the opening notes (incipit) or main theme of the work. Such catalogues can be used for many purposes, including as guides to a specific composer's works, as an inventory of a library's holding or as an advertisement of a publisher's output. In addition to the musical identification, a thematic catalogue may continue information such as dates of composition and first performance. Works within a thematic catalogue can be grouped chronologically or by genre.

Thematic catalogues produced as scholarly guides to the works of a particular composer provide a shorthand means of identification for their music. The Bach-Werke-Verzeichnis (BWV) numbering system used for the works of Johann Sebastian Bach

Johann Sebastian Bach

Johann Sebastian Bach was a German composer, organist, harpsichordist, violist, and violinist whose sacred and secular works for choir, orchestra, and solo instruments drew together the strands of the Baroque period and brought it to its ultimate maturity...

is one example.