The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with 1.2 billion members worldwide. It is among the oldest institutions in the world and has played a prominent role in the history of Western civilisation. The Catholic hierarchy is led by the Pope and includes cardinals, patriarchs and diocesan bishops. The Church teaches that it is the one true church divinely founded by Jesus Christ, that its bishops are the successors of Christ's apostles and that the Pope is the sole successor to Saint Peter who has apostolic primacy.

The Church maintains that the doctrine on faith and morals that it presents as definitive is infallible. There are a variety of doctrinal and theological emphases within the Catholic Church, including the Eastern Catholic Churches, the personal ordinariates and religious communities such as the Jesuits, the Franciscans and the Dominicans.

The Catholic Church is Trinitarian and defines its mission as spreading the Gospel of Jesus Christ, administering the sacraments and exercising charity. Catholic worship is highly liturgical, focusing on the Mass or Divine Liturgy during which the sacrament of the Eucharist is celebrated. The Church teaches that bread and wine used during the Mass become the body and blood of Christ through transubstantiation. The Catholic Church practises closed communion and only baptised members of the Church in a state of grace are ordinarily permitted to receive the Eucharist.

Catholic social teaching emphasises support for the sick, the poor and the afflicted through the corporal works of mercy. The Catholic Church is the largest non-government provider of education and medical services in the world. Catholic spiritual teaching emphasises spread of the Gospel message and growth in spiritual discipline through the spiritual works of mercy.

The Church holds the Blessed Virgin Mary, as mother of Jesus Christ, in special regard and has defined four specific Marian dogmatic teachings, namely her Immaculate Conception without original sin, her status as the Mother of God, her perpetual virginity and her bodily Assumption into Heaven at the end of her earthly life. Numerous Marian devotions are also practised.