Onan (, Modern Onan, Tiberian ʼÔnān ; "Strong") is a person in the Bible. He is in the Book of Genesis, chapter 38. He was the second son of Judah. Like his older brother, Er, Onan was killed by Yahweh. Onan's death was because he was "evil in the sight of the Lord" for being unwilling to father a child by his widowed sister-in-law.