Adult orbital xanthogranulomatous diseases are rare entities and encompass a group of disorders with varying manifestations that are poorly understood. Taken as a group, there are non-Langerhans histiocytic disorders (type II) that are diagnosed histologically by the presence of foamy histiocytes, Touton giant cells, and varying degrees of fibrosis. Based on the accompanying systemic associations, there are 4 main categories of adult xanthogranulomatous disease: adult-onset xanthogranuloma, adult-onset asthma and periocular xanthogranuloma, necrobiotic xanthogranuloma, and Erdheim–Chester disease. Herein, we discuss the etiopathogenesis, systemic associations, methods of diagnosis, and treatment options for these disorders.