Antinomianism (Ancient Greek: ἀντί [anti] "against" and νόμος [nomos] "law") is any view which rejects laws or legalism and argues against moral, religious or social norms (Latin: mores), or is at least considered to do so. The term has both religious and secular meanings.

In some Christian belief systems, an antinomian is one who takes the principle of salvation by faith and divine grace to the point of asserting that the saved are not bound to follow the moral law contained in the Ten Commandments. Antinomians believe that faith alone guarantees eternal security in heaven, regardless of one's actions.

The distinction between antinomian and other Christian views on moral law is that antinomians believe that obedience to the law is motivated by an internal principle flowing from belief rather than from any external compulsion. Antinomianism has been considered to teach that believers have a "license to sin" and that future sins don't require repentance. Johann Agricola, to whom Antinomianism was first attributed, stated "If you sin, be happy, it should have no consequence."

Examples of antinomians being confronted by the religious establishment include Martin Luther's critique of antinomianism and the Antinomian Controversy of the seventeenth-century Massachusetts Bay Colony. In Lutheranism and Methodism, antinomianism is a heresy.

By extension, the word "antinomian" is used to describe views in religions other than Christianity:

• the 10th century Sufi mystic al-Hallaj was accused of antinomianism
• the term is also used to describe certain practices or traditions in Frankism
• aspects of Vajrayana and Tantra that include sexual rituals are sometimes described as "antinomian" for Buddhism and Hinduism