Sacred mysteries are topics related to supernatural events connected to a god or religious belief and practices. Sacred mysteries can be one of two things:

A mystagogue or hierophant is a person who keeps and teaches secret knowledge about the first type of mysteries. Mysticism is described as a part of philosophy or religion that is concerned with the second type of mysteries.

Greece and Rome

The mystery religions of ancient times were secret religious groups that required people to be initiated to join. Some had different levels of initiation and taught beliefs that were kept secret and needed supernatural explanations. In some groups, only priests knew parts of the teachings. These included the Eleusinian Mysteries, Mithraism, the Cult of Isis, and the Cult of Sol Invictus. Mystery traditions were common in ancient Greece and during the peak of the Roman Empire. Some parts of Early Christianity also used secrecy in a similar way.

Today, Pietas Comunità Gentile helps keep ancient mystery cults alive by organizing events like the Dionisiache, which take place in the cloister of the old Convent of the Reformed Fathers in Pulsano. These events work with local groups and the Pulsano Archaeological Museum. The Dionisiache honored Artemis and Dionysus and used symbols and rituals to revive Roman religion. Activities included shamanic drumming, sacred songs, and nighttime rituals under the moon. As a national and international group, Pietas has also built two temples in the Ionian region dedicated to Apollo and Minerva. These temples encourage the revival of worshiping gods and their hidden symbols.

Christianity

The Greek word "mysterion" appears 27 times in the New Testament. According to Strong's Concordance, this word (Strong's #3466) refers to a secret that can only be understood if God reveals it. Its meaning is closer to the idea of "mystical" (something beyond human understanding) than to the modern word "mystery" (something not understood). In biblical Greek, the term describes something that needs to be explained or made clear.

Most Christian traditions believe that certain ideas in Christian theology, such as the nature of the Trinity, the birth of Jesus from a virgin, and the resurrection of Jesus, cannot be fully explained by human reasoning. These ideas are considered deeper than simple secrets.

In the Catholic Church, the Latin word "mysterium fidei" means "mystery of faith." The Catechism of the Catholic Church (1997) explains that this refers to truths hidden in God that can only be known if God reveals them.

The First Vatican Council (1869–1870) confirmed that some truths in Christian faith are mysteries that cannot be fully understood through human reason alone. It stated that if someone claimed all religious truths could be explained without God’s revelation, that person would be considered outside the Church. Other Christian traditions share this belief, even if they use different terms.

In early Christian times, some teachings and practices, such as sacraments and rituals, were kept secret from non-Christians to avoid mockery. These were gradually shared with new believers. Over time, secrecy decreased, but the word "mystery" remained important. In Eastern Orthodox churches, the term "mystery" is used for both sacraments and other sacred practices. In Western churches, sacraments are often called "sacraments," though they are also seen as mysteries. For example, the Catholic Church teaches that the Eucharist (Holy Communion) is a mystery because it involves the transformation of bread and wine into the body and blood of Jesus. Pope Paul VI’s 1965 encyclical on the Eucharist was titled Mysterium fidei, meaning "Mystery of Faith."

In Catholic Mass, the priest says "The mystery of faith" during the Eucharist. The word "mystery" was once used broadly for all sacraments in both Eastern and Western traditions, as seen in writings by early Christian leaders like St. Cyril of Jerusalem and St. Ambrose of Milan.

While all official Christian teachings are now public, a field called "Christian mysticism" focuses on personal reflections about sacred mysteries. These mysteries are considered too deep for full human understanding.

In Eastern Christianity, the term "mystery" refers to what Western churches call "sacraments" and "sacramentals." Western churches have clearly defined seven sacraments in their laws, such as Baptism and Marriage. Eastern churches do not define "mysteries" as precisely, though they also recognize seven major mysteries, including Baptism, Chrismation (Confirmation), and Holy Communion. Orthodox Christians receive both bread and wine in the Eucharist and keep both in the church’s tabernacle. Sacred mysteries are described as holy actions through which the Holy Spirit gives spiritual strength to people.

Orthodox teachings list seven sacred mysteries, matching the seven Western sacraments: Baptism, Chrismation (Confirmation), Confession (Penance), Holy Communion (Eucharist), Marriage, Ordination (Holy Orders), and Unction (Anointing of the Sick). However, Orthodox theology does not limit the term "mystery" to these seven. All faithful people are expected to receive most of these, though marriage and ordination are not required for everyone. Women are not ordained as priests in Orthodox tradition but may become nuns.

Christian life centers on the mystery of Christ becoming human, uniting God and humanity. The process of spiritual growth, called theosis, continues today. The Sacraments, or Sacred Mysteries, help believers connect with God if received with faith and proper preparation. Christians believe God is present everywhere, but especially in the Sacred Mysteries.

Kallistos Ware, a theologian, wrote in The Orthodox Way about these ideas.