Antinomianism (from the Greek "against" + "law"), is a belief originating in Christian theology that faith alone, not obedience to religious law, is necessary for salvation. The concept is related to the foundational Protestant belief of Sola Fide, or justification through faith alone however, antinomianism represents an extreme of this idea, wherein adherence to the Mosaic Law is considered inessential in the Christian lifestyle, given the view that faith itself is sufficient to attain salvation. The concept is also related to the Biblical Greek terms anomia and anomos which are generally translated in English translations of the Bible as lawlessness and lawless respectively. An antinomian theology considers adherence to Mosaic Law unnecessary, but it does not usually imply the embrace of ethical permissiveness rather it usually implies emphasis on the inner working of the Holy Spirit as the primary source of ethical guidance. Antinomianism is the opposite of legalism or works righteousness the notion that obedience to a code of religious law earns salvation.

The term "antinomian" emerged soon after the Protestant Reformation (c.1517) and has historically been used mainly as a pejorative against Christian thinkers or sects who carried their belief in justification by faith further than was customary. For example, Martin Luther preached justification by faith alone, but was also an outspoken critic of antinomianism, perhaps most notably in his Against the Antinomians (1539). Few groups or sects, outside of Christian Anarchism or Jewish anarchism, explicitly call themselves "antinomian".

While the term originated in early controversies of Protestant doctrine, and has its roots in debates over the Synoptic Gospels and the Pauline Epistles and the issue of Paul of Tarsus and Judaism, it can be extended to any religious group believing they are not bound to obey the laws of their own religious tradition.