The Church Fathers, Early Church Fathers, Christian Fathers, or Fathers of the Church were ancient and influential Christian theologians and writers who established the intellectual and doctrinal foundations of Christianity. The historical period in which they worked became known as the Patristic Era and spans approximately from the late 1st to mid-8th centuries, flourishing in particular during the 4th and 5th centuries, when Christianity was in the process of establishing itself as the state church of the Roman Empire.

Sacred tradition, also called holy tradition or apostolic tradition, is a theological term used in Christian theology. According to this theological position, sacred Tradition and Scripture form one deposit, so sacred Tradition is a foundation of the doctrinal and spiritual authority of Christianity and of the Bible. Thus, the Bible must be interpreted within the context of sacred Tradition and within the community of the denomination. The denominations that ascribe to this position are the Catholic, Eastern Orthodox, and Oriental Orthodox churches, and the Assyrian churches.