Caïn may refer to:

• Henri Caïn (1857–1937), French dramatist, opera and ballet librettist
• French spelling of Cain, son of Adam and Eve

Cain is the first mentioned son of Adam and Eve in the Bible.

Cain and Abel ( Qayin, Heḇel; Qabeel, Habeel) were, according to the Book of Genesis, two sons of Adam and Eve. Cain is described as a crop farmer and his younger brother Abel as a shepherd. Cain was the first human born and Abel was the first human to die. Cain committed the first murder by killing Abel. Interpretations of Genesis 4 by ancient and modern commentators have typically assumed that the motives were jealousy and anger. The story of Cain and Abel is found in the Christian Bible, Jewish Torah and Muslim Quran.

CAIN (Conflict Archive on the Internet) is a database containing information about Conflict and Politics in Northern Ireland from 1968 to the present. The project began in 1996, with the website launching in 1997. The project is based within Ulster University at its Magee campus. The archive chronicles important events during the Troubles, stretching from 1968 until the present day.