List of landmark court decisions in the United States

The following is a partial list of landmark court decisions in the United States. Landmark decisions establish a significant new legal precedent or concept. They can also substantially change the interpretation of existing law. Such a decision may settle the law in more than one way:

• By distinguishing a new principle that refines a prior principle. This way it can depart from prior practice without violating the rule of stare decisis.
• Or, by establishing a test case (a case used to set a precedent) or a measurable standard that can be applied by courts in future decisions.

In the United States, landmark court decisions come most frequently from the Supreme Court. Sometimes United States courts of appeals make such decisions, particularly if the Supreme Court chooses not to review the case or if it adopts the holding of the lower court. Although many cases from state supreme courts are significant in developing the law of that state, only a few are so radically different that they announce standards that many other state courts then choose to follow.