in Christian doctrine, the condition or state of sin into which each human being is born; also, the origin (i.e., the cause, or source) of this state. Traditionally, the origin has been ascribed to the sin of the first man, Adam (Adam and Eve), who disobeyed God in eating the forbidden fruit (of knowledge of good and evil) and, in consequence, transmitted his sin and guilt by heredity to his descendants.

The doctrine has its basis in the Bible. Although the human condition (suffering, death, and a universal tendency toward sin) is accounted for by the story of the Fall of Adam in the early chapters of the book of Genesis, the Hebrew Scriptures say nothing about the transmission of hereditary sin to the entire human race. In the Gospels also there are no more than allusions to the notion of the Fall of Man and universal sin. The main scriptural affirmation of the doctrine is found in the writings of St. Paul (Paul, the Apostle, Saint) and particularly in Romans 5:12–19, a difficult passage in which Paul establishes a parallelism between Adam and Christ, stating that whereas sin and death entered the world through Adam, grace and eternal life have come in greater abundance through Christ.

The doctrine is the prerequisite for the Christian understanding of the meaning of Jesus' crucifixion and atonement. Despite its importance for understanding Jesus' sacrifice, the doctrine of original sin has been minimized since the European Enlightenment.