On 1 November 1950, Pope Pius XII issued the apostolic constitution Munificentissimus Deus, formally defining as Catholic dogma that Mary, the mother of Jesus, having completed the course of her earthly life, was assumed body and soul into heavenly glory. The definition drew on a long tradition of belief in Mary's bodily assumption reaching back through medieval and patristic theology to the ancient Eastern feast of the Dormition, while deliberately leaving open, unlike the Eastern tradition's more specific language, the question of whether Mary actually died before being assumed.
The definition followed an extensive process of consultation Pius XII had undertaken with Catholic bishops worldwide, seeking to confirm that belief in the Assumption was already effectively universal within Catholic teaching and popular devotion before formalizing it as binding dogma, a step intended to demonstrate that the definition articulated an already existing consensus rather than introducing a genuinely new teaching.
The dogma completed a doctrinal development regarding Mary that had proceeded gradually over many centuries, moving from widespread devotional belief and liturgical commemoration toward formal doctrinal definition, a pattern also visible in the earlier 1854 definition of the Immaculate Conception, the only other Marian dogma the Catholic Church has formally defined in comparable terms.