A living will is a legal document that allows you to express your wishes to doctors in case you become incapacitated. In a living will, you can outline whether or not you want your life to be artificially prolonged in the event of a devastating illness or injury.
A living will is often combined with a "health care proxy," which allows you to designate someone to make health care decisions for you if you become incapacitated. The living will and the health care proxy together make up what's called an "advanced health care directive." 
