Vasoactive Intestinal Peptide (VIP) is a 28-amino acid neuropeptide and hormone distributed widely throughout the nervous system, gastrointestinal tract, and immune tissues. It activates two primary receptor subtypes (VPAC1 and VPAC2) to exert potent vasodilatory, bronchodilatory, and immunomodulatory effects. VIP is a key anti-inflammatory neuropeptide — it suppresses pro-inflammatory cytokine production, promotes Th2 immune responses, and protects against autoimmune and inflammatory pathologies in preclinical models. Research has also examined its role in circadian rhythm regulation, neuroprotection, and pulmonary function.