Plain people are Christian groups in the United States, characterized by separation from the world and by simple living, including plain dressing in modest clothing. Many plain people have an Anabaptist background. These denominations are largely of German, Swiss German and Dutch ancestry, though people of diverse backgrounds have been incorporated into them. Conservative Friends are traditional Quakers who are also considered plain people; they come from a variety of different ethnic backgrounds.

Simple living refers to practices that promote simplicity in one's lifestyle. Common practices of simple living include reducing the number of possessions one owns, depending less on technology and services, and spending less money. In addition to such external changes, simple living also reflects a person's mindset and values. Simple living practices can be seen in history, religion, art, and economics.