Chronic Fatigue Syndrome (CFS) is a complex disorder characterized by intense fatigue that lasts for at least 6 months. The cause is unknown, though virus infection, stress, and toxins may play a role. While there is no diagnostic test, CFS can be diagnosed after ruling out other potential illnesses if a patient experiences fatigue plus symptoms like memory problems, muscle pain, headaches, and malaise following exertion. While CFS has no cure, treatment may involve counseling, cognitive behavioral therapy, exercise therapy, medications, and alternative therapies to help manage symptoms.