Swine Annexin V (also known as ANXA5, Annexin A5, placental anticoagulant protein I (PAP-I), lipocortin V, or anchorin CII) is a calcium-dependent phospholipid-binding protein belonging to the annexin family, which plays important roles in membrane organization, cellular signaling, inflammation, and regulation of apoptosis. In pigs (Sus scrofa domesticus), Annexin V binds with high affinity to phosphatidylserine exposed on the outer leaflet of the plasma membrane during early stages of apoptosis or cellular injury in the presence of calcium ions. Because of this property, FITC-labeled swine Annexin V (Annexin V–FITC) is widely used in flow cytometry and fluorescence microscopy assays to detect and quantify apoptotic cells. Conjugation with fluorescein isothiocyanate (FITC) enables fluorescent labeling of cells displaying externalized phosphatidylserine, allowing sensitive identification of early apoptotic cells, typically used alongside viability dyes such as propidium iodide (PI) or 7-AAD to distinguish early apoptosis from late apoptosis or necrosis. In swine health and research, Annexin V–FITC assays are used to study immune cell apoptosis during viral infections such as porcine reproductive and respiratory syndrome virus (PRRSV) and swine influenza, as well as to evaluate inflammatory responses, tissue injury, and drug-induced cytotoxicity. It is also applied in reproductive biology to assess sperm membrane integrity and early embryonic cell viability in assisted reproductive technologies. As a biomarker of apoptosis and membrane remodeling, swine Annexin V supports veterinary and translational research into host–pathogen interactions, immune regulation, and cell death pathways relevant to both livestock health and human disease models.