Osteomyelitis of the jaws is an inflammation and infection of the bone marrow, involving both the cortical and medullary portions, related to bacterial or fungal activity. The incidence is higher in the mandible due to its dense, poorly vascularized cortical plates. Acute and chronic forms exist, with chronic osteomyelitis characterized by low-grade inflammation and persistent infection. The most common forms are osteoradionecrosis (ORN) and medication-related osteonecrosis of the jaws (MRONJ). ORN is a feared complication of head and neck radiation therapy, with clinical diagnostic criteria including exposed necrotic bone within the radiation field, persisting for at least 3 months. MRONJ is a severe adverse drug reaction caused by antiresorptive (bisphosphonates and denosumab) or antiangiogenic medications, leading to progressive bone destruction in the maxillofacial region. Prevention strategies, staging, and treatment goals are discussed for both conditions. Odontogenic infections, such as pulpitis, periapical abscesses, granulomas, and cysts, can also lead to osteomyelitis. Differential diagnoses like condensing osteitis, diffuse sclerosing osteomyelitis, and osteomyelitis with proliferative periostitis are briefly covered.