The Paschal Triduum or Easter Triduum (Latin: Triduum Paschale), Holy Triduum (Latin: Triduum Sacrum), or the Three Days, is the Christian period of three days that begins with the liturgy on the evening of Maundy Thursday, reaches its high point in the Easter Vigil, and closes with evening prayer on Easter Sunday. It is a moveable observance recalling the Passion, Crucifixion, Death, burial, and Resurrection of Jesus, as portrayed in the canonical Gospels.

In the Anglican, Lutheran, Methodist, Moravian and Reformed traditions, the Paschal Triduum straddles the two liturgical seasons of Lent and Easter in the Church calendar (Holy Saturday is the last day of Lent, with the Easter Vigil being the first liturgy of Eastertide). In the Roman Catholic tradition since the 1955 reform by Pope Pius XII, the Easter Triduum has been more clearly distinguished as a separate liturgical period.

Previously, all these celebrations were advanced by more than twelve hours. The Mass of the Lord's Supper and the Easter Vigil were celebrated on the morning of Thursday and Saturday respectively, and Holy Week and Lent were seen as ending only on the approach of Easter. In the Roman Rite, after the Gloria in excelsis Deo in the Mass of the Lord's Supper, all church bells are silenced (sometimes replaced by a crotalus) and the organ is not used. This period that lasted from Thursday morning to before Easter Sunday began what was once referred to in Anglo-Saxon times as "the still days". Weddings in the Catholic Church were once prohibited throughout Lent and certain other times of the year as well, and are still forbidden during the Triduum. Lutherans still discourage weddings during the entirety of Holy Week, inclusive of the Easter Triduum.

In some Protestant denominations, the Triduum begins with an evening worship service on Maundy Thursday.

In the Catholic Church and in the Anglo-Catholic tradition of Anglicanism, in the Mass of the Lord's Supper, during the Gloria in Excelsis Deo, all church bells may be rung and the organ played; afterwards, bells and organ are silenced until the Gloria of the Easter Vigil. After the homily or sermon of the Mass, "where a pastoral reason suggests it", a ritual washing of the feet follows. The Mass concludes with a procession of the Blessed Sacrament to the altar of repose. This is usually followed by the stripping of the altars. Eucharistic adoration is encouraged after this, but if continued after midnight should be done without outward solemnity.

In the form of the Roman Rite in use before 1955, Mass was celebrated in the morning. Some faithful travelled to several churches to pray at each one's Altar of Repose, a practice called Seven Churches Visitation, which may also be done on Good Friday. The Mass included no washing of the feet, which could instead be done in a separate ceremony later in the day. The Mass itself concluded with a ritual stripping of all altars except the altar of repose, leaving only the cross and candlesticks. In the present form as revised in 1955, the altar is stripped bare without ceremony at some time after the evening Mass.

The liturgical colour for the Mass vestments and other ornaments is white in the Catholic and Anglican Churches. In the Lutheran Church, the liturgical colour for Maundy Thursday is scarlet or white. In the Reformed tradition, white or gold may be used. In the United Methodist Church, black is used as the liturgical colour.

On Good Friday, Christians recall the passion and crucifixion of Jesus.