All Saints Day is a solemn holy day of the Catholic Church celebrated annually on November 1. The day is dedicated to the saints of the Church, that is, all those who have attained heaven. The day is also commemorated by members of the Eastern Orthodox Church as well as some Protestant churches, such as Lutheran and Anglican churches. All Saints Day is a Catholic Holy Day of Obligation, meaning all Catholics are required to attend Mass on that day, unless they have an excellent excuse, such as serious illness.

The origin of All Saints Day can be traced back to the earliest Christians who annually honored their brothers and sisters who had given their lives while witnessing for and defending Jesus Christ. Typically, on the anniversary of a martyrs death, those living would gather to remember and offer prayers at the tomb or place where the deceased had died. In the fourth century, neighboring dioceses began to interchange feasts, to transfer relics, to divide them, and to join in a common feast, which led to a joint commemoration. In the persecution of Diocletian, the number of martyrs became so great that a separate day could not be assigned to each, but the Church appointed a common day for all.

All Saints Day is part of the season of Allhallowtide, which includes the three days from 31 October to 2 November inclusive, and in some denominations, such as Anglicanism, extends to Remembrance Sunday. In places where All Saints Day is observed as a public holiday but All Souls Day is not, cemetery and grave rituals such as offerings of flowers, candles, and prayers or blessings for the graves of loved ones often take place on All Saints Day.

In summary, All Saints Day is a Catholic Holy Day of Obligation celebrated annually on November 1, dedicated to the saints of the Church, and commemorated by members of the Eastern Orthodox Church as well as some Protestant churches. The day originated from the earliest Christians who annually honored their brothers and sisters who had given their lives while witnessing for and defending Jesus Christ. All Saints Day is part of the season of Allhallowtide, which includes the three days from 31 October to 2 November inclusive, and in some denominations, such as Anglicanism, extends to Remembrance Sunday.