Holy Week (Koinē Greek: Ἁγία καὶ Μεγάλη Ἑβδομάς, romanized: Agia ké Megale Evdomas, lit. 'Holy and Great Week') is the most sacred week in the liturgical year in Christianity. For all Christian traditions it is a moveable observance. In Eastern Christianity, which also calls it Great Week, it is the week following Great Lent and Lazarus Saturday, starting on the evening of Palm Sunday and concluding on the evening of Great Saturday. In Western Christianity, Holy Week is the sixth and last week of Lent, beginning with Palm Sunday and concluding on Holy Saturday.

Holy Week begins with the commemoration of Christ's triumphal entry into Jerusalem on Palm Sunday, marks the betrayal of Jesus on Spy Wednesday (Holy Wednesday), climaxing with the commemoration of the Mystical or Last Supper on Maundy Thursday and the Passion of Jesus on Good Friday. Holy Week concludes with Christ's rest in death and descent into Hades on Holy Saturday.

Christians believe that Jesus rested in death from the ninth hour (3 pm) on Good Friday until just before dawn on Sunday morning, the day of his resurrection from death, commonly known as Easter Sunday. However, in 1 Peter 3:19, there may be a clue as to a task Jesus performed during this period between death and resurrection: "By which also he went and preached unto the spirits in prison." This marks the beginning of the season of Eastertide, with its first week being known as Easter Week (Bright Week).

Holy Week liturgies generally attract the largest crowds of the year. Many Christian cultures have different traditions such as special liturgies or services, floats, sculptures or live reenactments of Christ's life, his arrest and crucifixion (also called the Lord's passion, the Passion of Christ or Passion of Jesus); the latter are known as Passion Plays, which are often interdenominational productions. In Eastern Rite Churches there are also many means to commemorate the Great Feasts and emphasize the theme of resurrection. Many television channels air films related to Holy Week, such as The Ten Commandments, The Greatest Story Ever Told and The Jesus Film.