Paraneoplastic neuronal autoantibodies (PNAs) constitute a heterogeneous group of immune biomarkers associated with paraneoplastic neurological syndromes (PNSs), which are remote cancer-associated neuroimmunological disorders resulting from antitumor immune responses directed against shared neuronal antigens rather than direct tumor invasion, metastasis, infection, ischemia, metabolic disturbances, or treatment toxicity. Recognition of these antibodies has fundamentally transformed understanding of neuro-oncology by establishing immune-mediated neuronal injury as a major mechanism linking systemic malignancies with central and peripheral nervous system dysfunction. Paraneoplastic neuronal autoantibodies target intracellular neuronal proteins, cytoplasmic antigens, synaptic proteins, ion channels, membrane receptors, and axonal structures. Classical onconeural antibodies include anti-Hu (ANNA-1), anti-Yo (PCA-1), anti-Ri (ANNA-2), anti-Ma2, anti-CV2/CRMP5, anti-amphiphysin, anti-Tr, anti-Zic4, anti-SOX1, anti-PCA2, and anti-recoverin, whereas neuronal surface antibodies comprise antibodies against N-methyl-D-aspartate receptor (NMDAR), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR), γ-aminobutyric acid receptors (GABAR), leucine-rich glioma-inactivated protein 1 (LGI1), and contactin-associated protein-like 2 (CASPR2). These antibodies exhibit strong associations with systemic malignancies including small-cell lung carcinoma, ovarian cancer, breast cancer, thymoma, testicular germ-cell tumors, and lymphomas. The pathogenesis involves ectopic neuronal antigen expression by tumors, loss of immune tolerance, antigen presentation, cytotoxic T-cell activation, intrathecal inflammation, blood–brain barrier dysfunction, and progressive neuronal injury. Antibodies directed against intracellular neuronal antigens predominantly reflect T-cell-mediated irreversible neuronal degeneration, whereas neuronal surface antibodies may directly alter receptor signaling and synaptic physiology and therefore demonstrate greater therapeutic reversibility. Clinically, paraneoplastic neuronal autoantibodies produce a broad spectrum of neurological syndromes including limbic encephalitis, cerebellar degeneration, sensory neuronopathy, encephalomyelitis, opsoclonus–myoclonus syndrome, retinopathy, autonomic dysfunction, peripheral neuropathies, movement disorders, and stiff-person syndrome. Early recognition is particularly important because neurological manifestations frequently precede tumor diagnosis and may represent the earliest indicator of occult malignancy. This descriptive review comprehensively examines the genetics, molecular genetics, classifications, epidemiology, pathogenesis, neurobiology, neurophysiology, immunopathology, clinical manifestations, diagnostic approaches, differential diagnoses, therapeutic strategies, prognosis, limitations, future directions, and emerging perspectives concerning paraneoplastic neuronal autoantibodies.