All Saints Day is a Christian holiday that honors all the saints of the church, both known and unknown, who have attained heaven. It is celebrated on November 1 in the Western churches and on the first Sunday after Pentecost in the Eastern churches. The holiday is part of a broader tradition that includes All Hallows Eve (Halloween) on October 31st and All Souls Day on November 2nd.

The origin of All Saints’ Day cannot be traced with certainty, and it has been observed on various days in different places. A feast of all martyrs was kept on May 13 in the Eastern church according to Ephraem Syrus (died c. 373), which may have determined the choice of May 13 by Pope Boniface IV when he dedicated the Pantheon in Rome as a church in honor of the Blessed Virgin and all martyrs in 609. The first evidence for the November 1 date of celebration and of the broadening of the festival to include all saints as well as all martyrs occurred during the reign of Pope Gregory III (731–741), who dedicated a chapel in St. Peter’s, Rome, on November 1 in honor of all saints. In 800 All Saints’ Day was kept by Alcuin on November 1, and it also appeared in a 9th-century English calendar on that day. In 837 Pope Gregory IV ordered its general observance.

All Saints Day is a holy day of obligation in the Roman Catholic Church, meaning all Catholics are required to attend Mass on that day, unless they have an excellent excuse, such as serious illness. In many traditions, All Saints Day is part of the season of Allhallowtide, which includes the three days from October 31 to November 2 inclusive.

Observances around the world include visiting cemeteries and graves of loved ones, offering flowers, candles, and prayers or blessings. In some schools, students dress up as saints for the day. The holiday is a time to remember and honor all the saints who have passed on to the Kingdom of Heaven.