An advance healthcare directive, also known as living will, personal directive, advance directive, medical directive or advance decision, is a legal document in which a person specifies what actions should be taken for their health if they are no longer able to make decisions for themselves because of illness or incapacity. In the U.S. it has a legal status in itself, whereas in some countries it is legally persuasive without being a legal document.

A living will is one form of advance directive, leaving instructions for treatment. Another form is a specific type of power of attorney or health care proxy, in which the person authorizes someone (an agent) to make decisions on their behalf when they are incapacitated. People are often encouraged to complete both documents to provide comprehensive guidance regarding their care, although they may be combined into a single form. An example of combination documents includes the Five Wishes in the United States. The term living will is also the commonly recognised vernacular in many countries, especially the U.K.