In the Roman Catholic Church, the Holy Days of Obligation are the days, other than Sundays, on which the faithful are required to attend Mass. The 1983 Code of Canon Law standardized ten days to be observed as Holy Days of Obligation throughout the Church. These days are:

• The Immaculate Conception (December 8)
• Christmas (Feast of the Nativity) (December 25)
• Mary, the Mother of God (January 1)
• Epiphany (January 6)
• St. Joseph (March 19)
• St. Peter and St. Paul (June 29)
• The Assumption of Mary (August 15)
• All Saints (November 1)
• The Ascension (39 days after Easter; 40th day of Eastertide)
• Corpus Christi (60 days after Easter)

Red vestments are worn at Mass held on the Feast of SS Peter and Paul. White vestments are worn at Mass held on all other holy days of obligation, even those which fall during a season of the liturgical year when some other colour is used.

Observation by country

The conference of bishops in a particular country or region may suppress the observance of these days, or transfer it to another day, with the permission of the Vatican. In some cases the obligation is observed during the following weekend mass. At times if a Holy Day is on a Monday or Saturday the observance will be held during regular weekend mass. They may also make the feast day of county's patron saint a holy day of obligation.

Australia

• Christmas
• The Epiphany (observed on following Sunday)
• The Assumption of Mary
• The Ascension (observed on following Sunday)
• Corpus Christi (observed on following Sunday)

Canada

• Christmas
• Mary, the Mother of God
• The Epiphany (observed on following Sunday)
• The Ascension (observed on following Sunday)
• Corpus Christi (observed on following Sunday)

England and Wales

• Christmas
• The Epiphany
• St. Peter and St. Paul
• The Assumption of Mary
• All Saints
• The Ascension
• Corpus Christi

Ireland

• The Immaculate Conception
• Christmas
• The Epiphany
• St. Patrick's Day
• The Assumption of Mary
• All Saints

Poland

• Christmas
• Mary, the Mother of God
• Epiphany
• The Assumption of Mary
• All Saints
• The Ascension (observed on following Sunday)
• Corpus Christi

United States

• The Immaculate Conception
• Christmas
• Mary, the Mother of God
• The Epiphany (observed on Sunday between Jan. 2 and Jan. 8)
• The Assumption of Mary
• All Saints Day
• The Ascension (observed on the following Sunday in the West)
• Corpus Christi (observed on following Sunday)

See also

• Liturgical year
• Moveable feast