The Living Constitution, or loose constructionism, is the claim that the United States Constitution and other constitutions hold a dynamic meaning that evolves and adapts to new circumstances even if the document is not formally amended. The Constitution is said to develop alongside the needs of a society and to provide a more malleable tool for governments. The idea is associated with views that contemporaneous society should be taken into account in the constitutional interpretation of phrases. The Constitution is referred to as the living law of the land as it is transformed according to necessities of the time and the situation.

The arguments for the Living Constitution vary but can generally be broken into two categories. First, the pragmatist view contends that interpreting the Constitution in accordance with its original meaning or intent is sometimes unacceptable as a policy matter and so an evolving interpretation is necessary. The second, relating to intent, contends that the constitutional framers specifically wrote the Constitution in broad and flexible terms to create such a dynamic, "living" document. Opponents of the idea often argue that the Constitution should be changed by an amendment process because allowing judges to change the Constitution's meaning undermines democracy. Another argument against the Living Constitution is that legislative action, rather than judicial decisions, better represent the will of the people in the United States in a constitutional republic since periodic elections allow individuals to vote on who will represent them in the United States Congress and members of Congress should (in theory) be responsive to the views of their constituents. That argument relies partly on the fact that federal judges, who are not elected but appointed by the President, have life tenure and so are far less at risk of losing their jobs than members of Congress, who are elected. The primary alternative to a living constitution theory is "originalism.'

Some supporters of the living method of interpretation, such as professors Michael Kammen and Bruce Ackerman, refer to themselves as organists.