The General Instruction of the Roman Missal (GIRM)—in the Latin original, Institutio Generalis Missalis Romani (IGMR)—is the detailed document governing the celebration of Mass of the ordinary form of the Roman Rite of the Catholic Church since 1969. It is printed at the start of recent editions of the Roman Missal.
This document unified and replaced a number of documents that were printed in earlier editions:
Rubricae Generales Missalis (General Rubrics of the Missal), amplified and revised by Pope Clement VIII in 1604 and completely rewritten by Pope John XXIII in 1960.
Additiones et Variationes in Rubricis Missalis ad normam Bullae "Divino afflatu" et subsequentium S. R. C. decretorum (Additions and Variations to the Rubrics of the Missal in accordance with the Bull Divino afflatu and subsequent decrees of the Sacred Congregation of Rites), which existed in Missals printed only between 1920 and 1962.
Ritus servandus in celebratione Missae (Rite to be observed in celebrating Mass), revised by Pope Clement VIII in 1604 and Pope John XXIII in 1962.
Structure
The General Instruction is arranged in nine chapters, preceded by a preamble. The chapter headings are:
The Importance and Dignity of the Eucharistic Celebration
The Structure of the Mass, Its Elements and Its Parts