The Ricordi Online Numerical Catalogue expresses and embodies the celebrated Milanese musical publishing house’s activity. All the works acquired by the company, founded by Giovanni Ricordi in 1808, are present in numerical order roughly corresponding to chronological order. They are described with their essential information for the identification of the compositions, including the sale prices at the dates of the publication of the catalogue’s two volumes, information that makes it possible to identify many first editions. The two volumes of the catalogue, an important bibliographic resource for the history of music and music publishing from 1808 to 1870 in Italy and Europe, are here made available online. They contain 43,025 entries. This online version may be consulted easily by catalogue number, by author, by the title of the composition, and by the date of publication (or acquisition) by the editor Ricordi.