OCTAVARIUM ROMANUM. — A liturgical book of the Roman Church, for optional use, containing the lessons of the Second and Third Nocturns to be read during the days of the particular octaves of the feasts of the patrons and titular saints of churches.
Once the norms for celebrating the particular octaves of the patrons and titular saints of churches had been definitively established by s. Pio V, with the publication of the reformed Breviary (1568) and Missal (1570), the lack of proper lessons for the weekdays of
OCTAVARIUM ROMANUM – Frontispiece of the Plantinian edition with symbolic representations of the number 8. Antwerp, ex officina Plantiniana Balthasaris Moreti V. 1661 – Rome, copy in the Library of the College of S. Alfonso.
these octaves, since the body of the Breviary lacks such lessons. To remedy this deficiency, the well-known liturgist Gavanto, consultor to the S. Congregation of Rites, set to work and composed a collection of patristic readings, specially arranged for the days of these particular octaves. The question then arose whether this collection should be incorporated directly into the Breviary or constitute a separate liturgical book. The S. Congregation decided to publish a book separate from the Breviary, and confirmed this decision by the decree of 19 February 1622, prefixed to the book that came to be called: O. R., published in Rome in 1623 and almost immediately thereafter also outside Rome in various editions. Gavanto prefaced it with a learned introduction, in which he dwells at length on the history and significance of the octaves; this introduction has remained in the modern editions. The two latest editions of the O. R. are those of Pustet, prepared by the S. Congregation of Rites itself, in 1882 and 1902, with an extensive appendix.
The O. R. is not strictly obligatory, but, in response to a question submitted to it, the S. Congregation of Rites replied that the lessons lacking for the particular octaves « desumantur ex O. R.» (Decr. auth. n. 2735; 8 August 1835).