Chronic fatigue syndrome (CFS) is a complex disorder characterized by extreme fatigue that lasts for at least six months and is not improved by rest. This fatigue often worsens with physical or mental activity, leading to significant limitations in daily activities. The exact cause of CFS is unknown, but it may involve a combination of factors, including viral infections, immune system issues, and hormonal imbalances. People with CFS may also experience other symptoms, such as sleep disturbances, cognitive difficulties, and muscle or joint pain. Diagnosis is challenging, as there are no specific tests for CFS, and it often requires ruling out other medical conditions. Treatment typically focuses on managing symptoms and improving quality of life.