Chronic fatigue syndrome (CFS) is an ongoing, debilitating disorder characterized by extreme fatigue that cannot be explained by any underlying medical condition. The fatigue associated with CFS is not alleviated by rest and can be severe enough to limit a person's ability to participate in daily activities. CFS often includes other symptoms, such as muscle and joint pain, headaches, sleep disturbances, and problems with concentration and memory.

The exact cause of CFS is not known, but it is thought to be related to an underlying biological or psychological condition that affects the body's ability to produce energy. Potential causes include inflammation, infection, and stress. Diagnosis of CFS is made based on a person's symptoms and the exclusion of other potential causes.

Treatment for CFS typically includes a combination of lifestyle changes, such as stress management and exercise, and medications to address any underlying medical conditions. Additional therapies, such as cognitive-behavioral therapy and acupuncture, may also be used to manage symptoms. With proper management, many people with CFS are able to experience improvement in their symptoms and lead a fulfilling life.