Hamster 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 hamsters (commonly Mesocricetus auratus and Phodopus spp.). Osteopontin interacts with integrins (such as αvβ3, αvβ1) and CD44 receptors, activating signaling pathways that regulate cell migration, inflammatory responses, and extracellular matrix remodeling. In hamsters, OPN is produced by osteoblasts, macrophages, epithelial cells, and activated T lymphocytes, and contributes to bone metabolism, immune activation, and tissue repair processes. In research, hamster osteopontin is particularly relevant in models of inflammation, fibrosis, and viral infection, including Syrian hamster models of respiratory diseases such as SARS-CoV-2, where OPN expression is associated with macrophage recruitment, lung inflammation, and tissue remodeling during infection and recovery. OPN also participates in wound healing and fibrotic responses, influencing fibroblast activation and extracellular matrix deposition. Because hamsters are widely used as translational models for infectious disease and inflammatory pathology, characterization of hamster osteopontin supports studies of immune signaling, macrophage-mediated inflammation, and tissue remodeling mechanisms relevant to human disease.