Bovine BAFF (B cell–Activating Factor), also known as BLyS or TNFSF13B, is a member of the tumor necrosis factor (TNF) superfamily and plays a critical role in B cell development, survival, and humoral immunity in cattle (Bos taurus). BAFF is produced primarily by monocytes, macrophages, dendritic cells, neutrophils, and certain stromal cells, and it signals through the receptors BAFF-R (TNFRSF13C), TACI (TNFRSF13B), and BCMA (TNFRSF17) to promote peripheral B cell maturation, immunoglobulin class switching, and maintenance of long-lived plasma cells. In cattle, BAFF supports antibody-mediated immunity in systemic and mucosal tissues, including the respiratory tract, gastrointestinal tract, and mammary gland. Dysregulated BAFF expression may contribute to chronic inflammation, persistent infection, or B cell proliferation in conditions such as bovine leukemia virus (BLV)–associated lymphoproliferative disease, mastitis, and other chronic infectious diseases. In veterinary and agricultural research, bovine BAFF is of particular interest in studies of vaccine-induced antibody responses, mucosal immunity, mastitis resistance, and comparative B cell biology. Characterizing BAFF signaling in cattle provides valuable insight into regulation of humoral immunity and strategies to enhance protective immune responses in livestock health and production systems.