Holy Week (Latin: Hebdomas Sancta or Hebdomas Maior, "Greater Week"; Greek: Ἁγία καὶ Μεγάλη Ἑβδομάς, Hagia kai Megale Hebdomas) in Christianity is the last week of Lent and the week before Easter. It includes the religious holidays of Palm Sunday, Maundy Thursday (Holy Thursday), Good Friday, and Holy Saturday. It does not include Easter Sunday. In Eastern Orthodox tradition, Holy Week starts on Lazarus Saturday, the day before Palm Sunday. (Easter Sunday, for context, is the first day of the new season of the Great Fifty Days, or Eastertide, there being fifty days from Easter Sunday to Pentecost Sunday.)

Holy Week in the Christian year is the week immediately before Easter. The earliest Catholic allusion to the custom of marking this week as a whole with special observances is to be found in the Apostolical Constitutions (v. 18, 19), dating from the latter half of the 3rd century and 4th century. In this text, abstinence from flesh is commanded for all the days, while for the Friday and Sunday an absolute fast is commanded. Dionysius Alexandrinus in his canonical epistle (AD 260), refers to the 91 fasting days implying that the observance of them had already become an established usage in his time.^[1]

Great Lent, or the Great Fast, is the most important fasting season in the church year in Eastern Christianity, which prepares Christians for the greatest feast of the church year, Pascha (Easter). In many ways Great Lent is similar to Lent in Western Christianity. There are some differences in the timing of Lent (besides calculating the date of Easter) and how it is practiced, both liturgically in the public worship of the church and individually.

One difference between Eastern Christianity and Western Christianity is the calculation of the date of Easter (see Computus). Most years, the Eastern Pascha falls after the Western Easter, and it may be as much as five weeks later; occasionally, the two dates coincide. Like Western Lent, Great Lent itself lasts for forty days, but unlike the West, Sundays are included in the count. Great Lent officially begins on Clean Monday, seven weeks before Pascha (Ash Wednesday is not observed in Eastern Christianity) and runs for 40 contiguous days, concluding with the Presanctified Liturgy on Friday of the Sixth Week. The next day is called Lazarus Saturday, the day before Palm Sunday. However, fasting continues throughout the following week, known as Passion Week or Holy Week, and does not end until after the Paschal Vigil early in the morning of Pascha (Easter Sunday).

Lent (Latin: Quadragesima, "fortieth"^[1]) is an observance in the liturgical year of many Christian denominations, lasting for a period of approximately six weeks leading up to Easter. In most Western denominations Lent is taken to run from Ash Wednesday to Maundy Thursday (Holy Thursday) or to Easter Eve.

The traditional purpose of Lent is the preparation of the believer—through prayer, penance, repentance, almsgiving, and self-denial. Its institutional purpose is heightened in the annual commemoration of Holy Week, marking the death and resurrection of Jesus, which recalls the events of the Passion of Christ on Good Friday, which then culminates in the celebration on Easter Sunday of the resurrection of Jesus Christ.