The Assumption of Mary into Heaven, informally known as The Assumption, according to the beliefs of the Roman Catholic Church, Eastern Orthodoxy, Oriental Orthodoxy, and parts of Anglicanism, was the bodily taking up of the Virgin Mary into Heaven at the end of her earthly life.
The Roman Catholic Church teaches as dogma that the Virgin Mary “having completed the course of her earthly life, was assumed body and soul into heavenly glory, thus the Assumption of Mary.” This doctrine was dogmatically defined by Pope Pius XII on November 1, 1950, in the Apostolic Constitution Munificentissimus Deus by exercising papal infallibility. While the Catholic Church and Eastern Orthodox Church believe in the Dormition of the Theotokos, which is the same as the Assumption of Mary, the death of Mary has not been dogmatically defined.
In Munificentissimus Deus (item 39) Pope Pius XII pointed to the Book of Genesis (3:15) as scriptural support for the dogma in terms of the Assumption of Mary and her victory over sin and death as also reflected in 1 Corinthians 15:54… “then shall come to pass the saying that is written, Death is swallowed up in victory”.
In the churches which observe it, the Assumption of Mary is a major feast day, commonly celebrated on August 15. In many Catholic countries, the feast is also marked as a Holy Day of Obligation.