Head and neck cancers comprise a heterogeneous group of malignancies arising from the oral cavity, pharynx, larynx, sinonasal tract, salivary glands, and related upper aerodigestive sites. In the United States, cancers of the oral cavity and pharynx account for approximately 2.9% of all new cancer diagnoses, with an estimated 60,480 new cases and 13,150 deaths in 2026. Despite advances in diagnosis, surgical technique, radiation delivery, systemic therapy, and supportive care, many patients continue to present with locoregionally advanced disease, and survival remains strongly influenced by tumor subsite, stage, nodal burden, extranodal extension, margin status, depth of invasion, human papillomavirus status, tobacco and alcohol exposure, and access to multidisciplinary care. Oral cavity squamous cell carcinoma remains primarily a surgically managed disease, with treatment guided by anatomic subsite, depth of invasion, clinical and pathologic nodal status, margin assessment, perineural and lymphovascular invasion, and adverse pathologic features. Contemporary management requires coordinated evaluation by head and neck surgical oncology, reconstructive surgery, radiation oncology, medical oncology, pathology, radiology, dentistry, speech and swallowing therapy, nutrition, rehabilitation, pain management, psychosocial oncology, and survivorship teams. Current guideline-based treatment integrates surgery, neck management, risk-adapted adjuvant radiation or chemoradiation, and—in selected locally advanced resectable head and neck squamous cell carcinoma—perioperative immunotherapy, supported by the phase III KEYNOTE-689 trial showing improved event-free survival with neoadjuvant and adjuvant pembrolizumab added to standard therapy. This review summarizes the contemporary epidemiology, staging, diagnostic workup, surgical principles, neck management, reconstructive considerations, indications for adjuvant therapy, systemic treatment advances, surveillance, survivorship, and multidisciplinary management of oral cavity and related head and neck cancers, with emphasis on evidence-based decision-making and functional outcomes.