In the Roman Catholic Church, an optional memorial is the lowest class of the feast day. The priest is permitted to celebrate the feast day or not as he chooses. (See Memorial.) The saints or events celebrated in these feast days are considered to be of less universal importance to the Church. In addition, as long as no feast day of higher rank is foreseen for a particular day, a priest is permitted to celebrate a feast day that does not appear in his local calendar as an optional memorial, normally out of personal devotion to the saint.
A list of all optional memorials in the universal calendar of the Catholic Church can be found at Calendar of Saints.
