Easter (Pascha; Greek Πάσχα Paskha, from פֶּסַח Pesaḥ) is a Christian festival and holiday celebrating the resurrection of Jesus Christ on the third day after his crucifixion at Calvary as described in the New Testament. Easter is the culmination of the Passion of Christ, preceded by Lent, a forty-day period of fasting, prayer, and penance. The last week of Lent is called Holy Week, and it contains the days of the Easter Triduum, including Maundy Thursday (also known as Holy Thursday), commemorating the Last Supper and its preceding foot washing, as well as Good Friday, commemorating the crucifixion and death of Jesus. Easter is followed by a fifty-day period called Eastertide, or the Easter Season, ending with Pentecost Sunday.

Easter is a moveable feast, meaning it is not fixed in relation to the civil calendar. The First Council of Nicaea (325) established the date of Easter as the first Sunday after the full moon (the Paschal Full Moon) following the March equinox. Ecclesiastically, the equinox is reckoned to be on 21 March (even though the equinox occurs, astronomically speaking, on 20 March in most years), and the "Full Moon" is not necessarily the astronomically correct date. The date of Easter therefore varies between 22 March and 25 April. Eastern Christianity bases its calculations on the Julian calendar, whose 21 March corresponds, during the 21st century, to 3 April in the Gregorian calendar, in which the celebration of Easter therefore varies between 4 April and 8 May.

Easter is linked to the Jewish Passover by much of its symbolism, as well as by its position in the calendar. In many languages, the words for "Easter" and "Passover" are etymologically related or homonymous. Easter customs vary across the Christian world, but attending sunrise services, exclaiming the Paschal greeting, clipping the church and decorating Easter eggs, a symbol of the empty tomb, are common motifs. Additional customs include egg hunting, the Easter Bunny, and Easter parades, which are observed by both Christians and some non-Christians.