Background: Primary adrenal insufficiency (PAI), commonly known as Addison’s disease, is a rare but potentially life threatening endocrine disorder resulting from destruction of the adrenal cortex and consequent deficiency of glucocorticoids, mineralocorticoids, and adrenal androgens. Autoimmune adrenalitis represents the leading cause in developed countries. Objective: This narrative review aims to summarize current knowledge regarding the epidemiology, pathophysiology, immunological mechanisms, clinical manifestations, diagnostic approach, and management strategies of Addison’s disease. Methods: A narrative literature review was conducted based on key articles, international clinical guidelines, and major reviews published in peer reviewed journals focusing on primary adrenal insufficiency. Results: Addison’s disease typically presents with nonspecific symptoms such as fatigue, weight loss, hypotension, and hyperpigmentation, often leading to delayed diagnosis. Laboratory findings include low serum cortisol, elevated adrenocorticotropic hormone (ACTH), electrolyte disturbances, and the presence of adrenal autoantibodies, particularly 21 hydroxylase antibodies. Lifelong hormone replacement therapy with glucocorticoids and mineralocorticoids remains the cornerstone of management. Failure to recognize or adequately treat the condition may result in adrenal crisis, a medical emergency associated with significant morbidity and mortality. Conclusion: Early recognition of Addison’s disease, appropriate diagnostic evaluation, and patient education regarding lifelong therapy and stress dose adjustment are essential to improve outcomes and quality of life.