"An eye for an eye" (Biblical Hebrew: עַיִן תַּחַת עַיִן, ʿayīn taḥaṯ ʿayīn) is a commandment found in the Book of Exodus 21:23–27 expressing the principle of reciprocal justice measure for measure. The earliest known use of the principle appears in the Code of Hammurabi, which predates the Hebrew Bible.

The law of exact retaliation (Latin: lex talionis) bears the same principle that a person who has injured another person is to be penalized to a similar degree by the injured party. In softer interpretations, it means the victim receives the [estimated] value of the injury in compensation. The intent behind the principle was to restrict compensation to the value of the loss.