The communion of saints is the theological understanding that believers form one body in Christ, united through the love and praise of the Most Holy Trinity (LG 3, CCC 960-962). This communion encompasses three states of the Church: those who are pilgrims on earth, those being purified after death, and those who have attained glory (CCC 955). Because all members of the Church share in charity toward God and one another, the union between wayfarers and those who have died is not interrupted but is instead reinforced by a continuous exchange of spiritual goods (CCC 956).

Catholics pray to the saints to seek their intercession, as those in heaven intercede with God on behalf of the living by offering the merits they acquired through Christ to help alleviate human weakness (CCC 957). This form of intercession is a prayer of petition that participates in the overarching intercession of Jesus Christ, the one mediator who lives to make intercession for all people with the Father (CCC 2634, Hebrews 7:25). This communion with the saints is intended to join the faithful closer to Christ, who is the fountain and head of all grace (CCC 958).

The communion of saints also provides spiritual guidance and a model for Christian living through the example of the saints’ lives, writings, and prayers (CCC 2683-2684). Within this tradition, prayer is often made in communion with Mary, who cooperates with the action of the Holy Spirit and serves as a model for entrusting supplications and praises to God (CCC 2674). Mary is transparent to Jesus and shows the way to him, magnifying God for his great works while entrusting the needs of believers to her as the Mother of Jesus (CCC 2674).

This spiritual connection is further manifested in the practice of praying for the dead, which can help them and make their own intercession effective since they remain part of the Mystical Body of Jesus Christ (CCC 959). In the life of the Church, this devotion is often expressed through the visitation of shrines and sanctuaries, which are places of hope where pilgrims entrust their prayers to the intercession of saints to experience the mercy of God (CCC 2688). Through these practices, the Church remains united with the saints through prayer (CCC 2692).