The Living Constitution, or judicial pragmatism, is the viewpoint that the U.S. constitution holds a dynamic meaning even if the document is not formally amended. Proponents view the constitution as developing alongside society's needs and provide a more malleable tool for governments. The idea is associated with views that contemporary society should be considered 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. Some supporters of the living method of interpretation, such as professors Michael Kammen and Bruce Ackerman, refer to themselves as organicists.

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 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. The primary alternative to a living constitution theory is "originalism." Opponents of the Living Constitution often regard it as a form of judicial activism.

Legal theorist Martin David Kelly argues that the question of whether a provision of a constitution (or of legislation, or of other kinds of texts or 'utterances' more generally) should be given its original or current meaning (the 'meaning issue') arises only if it is capable of applying across time (i.e. its application is not limited to the moment in time when it was made). Kelly argues that most constitutional (and statutory) provisions are 'always speaking'—they are operative on an ongoing basis, indefinitely—and so the meaning issue is a live one; but that some constitutional (and statutory) provisions are 'momentary' and so there is no basis for giving them a dynamic meaning. This point, Kelly argues, undermines some leading arguments against dynamic interpretation.

During the Progressive Era, many initiatives were promoted and fought for but prevented from full fruition by legislative bodies or judicial proceedings. One case in particular, Pollock v. Farmers' Loan & Trust Co., enraged early progressive activists hoping to achieve an income tax. That led progressives to the belief that the Constitution was unamendable and ultimately for them to find a new way to achieve the desired level of progress. Other proposals were considered, such as making the amending formula easier.

The phrase originally derives from the title of a 1927 book of that name by Professor Howard Lee McBain, and early efforts at developing the concept in its modern form have been credited to figures like Oliver Wendell Holmes Jr., Louis D. Brandeis, and Woodrow Wilson. The earliest mentions of the Constitution as "living," particularly in the context of a new way of interpreting it, comes from Woodrow Wilson's book Constitutional Government in the United States in which he wrote:

Living political constitutions must be Darwinian in structure and in practice.

Wilson strengthened that view, at least publicly, while he campaigned for president in 1912: