The Dormition of the Mother of God is a Great Feast of the Eastern Orthodox, Oriental Orthodox, and Eastern Catholic Churches (except the East Syriac churches). It celebrates the "falling asleep" (death) of Mary the Theotokos ("Mother of God", literally translated as God-bearer), and her being taken up into heaven. The Feast of the Dormition is observed on August 15, which for the churches using the Julian calendar corresponds to August 28 on the Gregorian calendar. The Armenian Apostolic Church celebrates the Dormition not on a fixed date, but on the Sunday nearest 15 August. In Western Churches the corresponding feast is known as the Assumption of Mary, with the exception of the Scottish Episcopal Church, which has traditionally celebrated the Falling Asleep of the Blessed Virgin Mary on August 15.

Christian canonical scriptures do not record the death or Dormition of Mary. Hippolytus of Thebes, a 7th- or 8th-century author, writes in his partially preserved chronology of the New Testament that Mary lived for 11 years after the death of Jesus, dying in AD 41.

The use of the term dormition expresses the belief that the Virgin died without suffering, in a state of spiritual peace. This belief does not rest on any scriptural basis, but is affirmed by Orthodox sacred tradition. Some apocryphal writings testify to this opinion, though neither the Orthodox Church nor other Christians accord them scriptural authority. The Orthodox understanding of the Dormition is compatible with Roman Catholic teaching, and was the dominant belief within the Western Church until late in the Middle Ages, when the slightly different belief in the bodily Assumption of Mary into heaven began to gain ground. Pope Pius XII declared the latter a dogma of the Catholic Church in 1950.

The Feast of the Dormition is preceded by a two-week fast, referred to as the Dormition Fast. From August 1 to August 14 (inclusive) Orthodox and Eastern Catholics fast from red meat, poultry, meat products, dairy products (eggs and milk products), fish, oil, and wine. In churches that follow the old or Julian Calendar, the fast is from August 14 to August 28. In the Coptic Orthodox Church, Ethiopian Orthodox Tewahedo Church and the Eritrean Orthodox Tewahedo Church, whose calendar is generally consistent with the Julian Calendar, the dates of the fast are from August 7 to August 22.

The Dormition Fast is a stricter fast than either the Nativity Fast (Advent) or the Apostles' Fast, with only wine and oil (but no fish) allowed on weekends. As with the other Fasts of the Church year, there is a Great Feast that falls during the Fast; in this case, the Transfiguration (August 6), on which fish, wine and oil are allowed.

In some places, the services on weekdays during the Dormition Fast are similar to the services during Great Lent (with some variations).

Many churches and monasteries in the Russian tradition perform the Lenten services on at least the first day of the Dormition Fast. In the Greek tradition, during the Fast either the Great Paraklesis (Supplicatory Canon) or the Small Paraklesis is celebrated every evening except Saturday evening and the Eves of the Transfiguration and the Dormition.^{[citation needed]}

The first day of the Dormition Fast is a feast day called the Procession of the Cross (August 1), on which day it is customary to have an outdoor procession and perform the Lesser Blessing of Water. In Eastern Orthodoxy it is also the day of the Holy Seven Maccabees, Martyrs Abimus, Antonius, Gurias, Eleazar, Eusebonus, Alimus, and Marcellus, their mother Solomonia, and their teacher Eleazar. Therefore, the day is sometimes referred to as "Makovei". Finally it is also considered the First of the three "Feasts of the Saviour" in August, the Feast to the All-Merciful Saviour and the Most Holy Mother of God.