In the biblical Book of Genesis, Cain and Abel are the first two sons of Adam and Eve. Cain, the firstborn, was a farmer, and his brother Abel was a shepherd. The brothers made sacrifices, each from his own fields, to God. God had regard for Abel's offering, but had no regard for Cain's. Cain killed Abel and God considered it murder, cursing Cain and sentencing him to a life of transience. Cain then dwelt in the land of Nod (נוֹד, 'wandering'), where he built a city and fathered the line of descendants beginning with Enoch. Thus, Cain was the first person born, and Abel the first to die.

The New Testament Epistle to the Hebrews interprets Abel’s sacrifice as more acceptable than Cain’s because it was offered in faith, earning Abel the approval of God. In the Qur'an, Cain and Abel are known as Qābīl (Arabic: قابيل) and Hābīl (هابيل), respectively. In Islamic tradition, the story of Cain and Abel portrays Cain as the first murderer driven by jealousy and lust, guided by the devil, and punished with guilt and disgrace, with some scholars debating the identity and motives of the brothers. In the Sethian Apocryphon of John, Cain and Abel are Archons, children of the Demiurge Yaldabaoth, named Yahweh and Elohim but called Cain and Abel to deceive.

The story of Cain and Abel is widely interpreted in academic biblical scholarship as a symbolic tale reflecting early agricultural society’s tensions—such as those between nomadic herders and settled farmers—and may draw from the older Mesopotamian myth Enlil Chooses the Farmer-God. Cain and Abel have become enduring cultural symbols of fratricide and sibling conflict, referenced and reinterpreted across art, literature, theater, music, and film from medieval times to modern popular culture.

The story of Cain's murder of Abel and its consequences is told in Genesis 4:1–18:

Now the man knew his wife Eve, and she conceived and bore Cain, saying, "I have produced a man with the help of the Lord." Next she bore his brother Abel. Now Abel was a keeper of sheep, and Cain a tiller of the ground. In the course of time Cain brought to the Lord an offering of the fruit of the ground, and Abel for his part brought of the firstlings of his flock, their fat portions. And the Lord had regard for Abel and his offering, but for Cain and his offering he had no regard. So Cain was very angry, and his countenance fell. The Lord said to Cain,

"Why are you angry,
and why has your countenance fallen?
If you do well,
will you not be accepted?
And if you do not do well,
sin is lurking at the door;
its desire is for you,
but you must master it."

Cain said to his brother Abel, "Let us go out to the field." And when they were in the field, Cain rose up against his brother Abel, and killed him.

Then the Lord said to Cain, "Where is your brother Abel?" He said, "I do not know; am I my brother's keeper?" And the Lord said, "What have you done? Listen; your brother's blood is crying out to me from the ground! And now you are cursed from the ground, which has opened its mouth to receive your brother's blood from your hand. When you till the ground, it will no longer yield to you its strength; you will be a fugitive and a wanderer on the earth." Cain said to the Lord, "My punishment is greater than I can bear! Today you have driven me away from the soil, and I shall be hidden from your face; I shall be a fugitive and a wanderer on the earth, and anyone who meets me may kill me." Then the Lord said to him, "Not so! Whoever kills Cain will suffer a sevenfold vengeance." And the Lord put a mark on Cain, so that no one who came upon him would kill him.