Equine Stem Cell Factor (SCF) (also known as KIT ligand, KITLG, mast cell growth factor, or steel factor) is a cytokine and growth factor that plays an important role in hematopoiesis, stem cell maintenance, and immune cell development in horses (Equus caballus). SCF belongs to a group of hematopoietic growth factors that regulate the survival, proliferation, and differentiation of stem and progenitor cells. It functions by binding to the c-Kit receptor (CD117), a receptor tyrosine kinase expressed on hematopoietic stem cells, mast cells, melanocytes, and germ cells, activating intracellular signaling pathways such as PI3K/AKT, MAPK, and JAK/STAT that regulate cell survival, proliferation, and differentiation. In horses, SCF is produced by stromal cells, fibroblasts, endothelial cells, and epithelial cells, and exists in both membrane-bound and soluble forms, allowing both localized and systemic regulation of c-Kit–expressing cells. Equine SCF contributes to bone marrow hematopoiesis, mast cell development, pigmentation, and reproductive cell biology, and plays a role in maintaining the hematopoietic stem cell niche. Because horses are increasingly studied in regenerative medicine and stem cell–based therapies, characterization of equine SCF supports research on hematopoietic stem cell regulation, tissue regeneration, and immune cell development, with relevance to equine health, wound healing, and musculoskeletal repair.