Brown tumors are uncommon, reactive bone lesions that develop as a consequence of prolonged hyperparathyroidism. Persistently elevated parathyroid hormone (PTH) levels stimulate excessive osteoclastic bone resorption and fibrous tissue proliferation, leading to focal bone loss and cyst-like osseous lesions. Histologically, these lesions represent manifestations of advanced osteitis fibrosa cystica, characterized by active osteoclastic resorption alongside reparative osteoblastic activity. Clinically, brown tumors may resemble primary bone neoplasms on imaging, making biochemical and endocrine laboratory correlation essential for accurate diagnosis. This chapter discusses their pathogenesis, radiologic and histopathologic characteristics, differential diagnosis, and current management strategies.