The Catholic Church teaches that Christians are obligated to observe Sunday—the Lord's Day (Dies Domini)—as the Christian fulfillment of the Old Testament Sabbath. The Sabbath commandment is transferred to Sunday (the day of the Resurrection) rather than Saturday in Catholic teaching. The precept of attending Mass on Sundays and holy days of obligation is among the chief precepts of the Church; missing Sunday Mass without a grave reason is considered a mortal sin.

Sunday is to be kept as a day of rest from unnecessary work, prayer, and family life, as well as charitable activities. Pope John Paul II's Apostolic Letter Dies Domini (1998) provides the fullest Catholic treatment of Sunday's theological significance. The Catechism (§§2174–2188) treats Sunday as 'the most important of all holy days' and a foretaste of the eternal rest of heaven. The Church celebrates a rich liturgical calendar of feast days in addition to Sundays.