This chapter provides an overview of orthorexia, a relatively new disease included within the broader category of eating disorders. The term orthorexia derives from the combination of two Greek words: orthos, meaning "healthy/correct" and oreksis, meaning "appetite." It is used to describe an unhealthy obsession with eating only healthy and natural food. A series of worries are related to this phenomenon: some preoccupations are expressly rooted in cultural and social contexts that reinforce the importance of healthy eating. For example, certain food items may be invested with alleged curative power and almost miraculous properties in some environments. Such views can discourage individuals from having a spontaneous and direct relationship with food because foods may be chosen only for their supposed healing properties rather than their taste. Theories, clinical cases, and scientific studies about this topic are presented.