Bovine Osteopontin (OPN) (also known as SPP1, Secreted Phosphoprotein 1, bone sialoprotein I, ETA-1, or early T-lymphocyte activation-1) is a multifunctional phosphorylated glycoprotein involved in immune regulation, cell adhesion, and tissue remodeling in cattle (Bos taurus). Osteopontin interacts with integrins (such as αvβ3 and αvβ1) and CD44 receptors, promoting signaling pathways that regulate cell migration, inflammation, and extracellular matrix remodeling. In cattle, OPN is produced by a variety of cells including osteoblasts, macrophages, epithelial cells, and activated T lymphocytes, and plays important roles in bone remodeling, immune responses, and reproductive biology. In bovine health, osteopontin is highly expressed in the mammary gland and uterine endometrium, where it contributes to embryo implantation, placental development, and early pregnancy maintenance, making it an important molecule in bovine fertility and reproductive success. OPN is also involved in inflammatory responses during mastitis and other infections, where it helps regulate leukocyte recruitment and cytokine signaling. While osteopontin supports tissue repair and immune defense, excessive expression may contribute to chronic inflammation or fibrotic tissue remodeling. As a regulator of immune cell migration, tissue remodeling, and reproductive signaling, bovine osteopontin is widely studied in host–pathogen interactions, mammary gland immunity, and reproductive physiology, contributing to improved understanding of cattle health, fertility, and productivity.