All Saints' Day is a solemn holy day of the Catholic Church celebrated annually on November 1st. The day is dedicated to the saints of the Church, that is, all those who have attained heaven. It should not be confused with All Souls' Day, which is observed on November 2nd, and is dedicated to those who have died and not yet reached heaven.

Although millions, or even billions of people may already be saints, All Saints' Day observances tend to focus on known saints --that is those recognized in the canon of the saints by the Catholic Church. All Saints' Day is also commemorated by members of the Eastern Orthodox Church as well as some protestant churches, such as Anglican, Lutheran and Anglican churches. Generally, 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. Other countries have different rules according to their national bishop's conferences. The bishops of each conference have the authority to amend the rules surrounding the obligation of the day. All Saints' Day was formally started by Pope Boniface IV, who consecrated the Pantheon at Rome to the Virgin Mary and all the Martyrs on May 13th in 609 AD. Boniface IV also established All Souls' Day, which follows All Saints.