Bovine CXCL4 (C-X-C motif chemokine ligand 4), also known as Platelet Factor 4 (PF4), is a CXC chemokine primarily released from α-granules of activated platelets and belonging to the platelet chemokine subgroup of the CXC chemokine family. In cattle (Bos taurus), CXCL4 is produced mainly by platelets and megakaryocytes and is released during platelet activation, vascular injury, or inflammation. CXCL4 plays roles in regulating coagulation, modulating inflammatory responses, and influencing leukocyte recruitment, particularly affecting monocytes, neutrophils, and other immune cells. It can also interact with glycosaminoglycans on endothelial cells and platelets, helping regulate platelet aggregation, vascular repair, and immune cell signaling at sites of tissue damage. In bovine health, CXCL4 is involved in inflammatory and thrombotic processes, including those occurring during infection, tissue injury, and inflammatory diseases such as mastitis or systemic inflammatory responses, where platelet activation and immune cell recruitment contribute to host defense and tissue repair. Because platelet-derived chemokines influence both hemostasis and immune regulation, bovine CXCL4 is studied in veterinary immunology, inflammation research, and host–pathogen interaction studies to better understand platelet–immune system interactions and inflammatory signaling in cattle.