Mystery Diagnosis is a television program that airs on the OWN: Oprah Winfrey Network. Each episode focuses on two or more individuals and their struggles to find out what ailments they suffer from. As the program's title suggests, doctors have a difficult time finding a diagnosis, often due to nonspecific symptoms, the rarity of the condition or disease, or the patient's case being an unusual manifestation of said condition or disease.

The series debuted on Discovery Health Channel in 2005, and was continued when the Oprah Winfrey Network replaced Discovery Health on January 1, 2011; the current season premiered January 5, 2011.