In United States copyright law, transformation is a possible justification that use of a copyrighted work may qualify as fair use, i.e., that a certain use of a work does not infringe its holder's copyright due to the public interest in the usage. Transformation is an important issue in deciding whether a use meets the first factor of the fair-use test, and is generally critical for determining whether a use is in fact fair, although no one factor is dispositive. Transformativeness is a characteristic of such derivative works that makes them transcend, or place in a new light, the underlying works on which they are based. In computer- and Internet-related works, the transformative characteristic of the later work is often that it provides the public with a benefit not previously available to it, which would otherwise remain unavailable. Such transformativeness weighs heavily in a fair use analysis and may excuse what seems a clear copyright infringement from liability.

In United States patent law the term also refers to the test set in In re Bilski: that a patent-eligible invention must "transform a particular article into a different state or thing".