Swine BAFF (B cell–Activating Factor), also known as BLyS or TNFSF13B, is a member of the tumor necrosis factor (TNF) superfamily and plays a central role in B cell development, survival, and regulation of humoral immunity in pigs (Sus scrofa). BAFF is produced primarily by monocytes, macrophages, dendritic cells, neutrophils, and certain stromal and epithelial cells, and it signals through the receptors BAFF-R (TNFRSF13C), TACI (TNFRSF13B), and BCMA (TNFRSF17) to promote transitional and mature B cell survival, immunoglobulin class switching, and maintenance of long-lived plasma cells. In swine, BAFF supports systemic and mucosal antibody responses, including IgA production in the respiratory and gastrointestinal tracts, which are critical for defense against enteric and respiratory pathogens. Dysregulated BAFF expression may contribute to chronic inflammation, persistent infection, or abnormal B cell activation in porcine disease models. In veterinary and translational research, swine BAFF is of particular interest in studies of vaccine-induced immunity and infectious diseases such as porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), African swine fever virus (ASFV), and enteric pathogens, as well as in comparative immunology due to physiological similarities between pigs and humans. Characterizing BAFF signaling in swine provides valuable insight into regulation of humoral immunity and strategies to enhance protective antibody responses in both agricultural and biomedical research settings.