Equine Erythropoietin (EPO) is a glycoprotein hormone belonging to the type I cytokine family that regulates erythropoiesis, the production of red blood cells. In horses (Equus caballus), erythropoietin is produced primarily by peritubular interstitial cells in the kidney, with smaller amounts synthesized in the liver, in response to hypoxia or reduced oxygen-carrying capacity of the blood. Equine EPO binds to the erythropoietin receptor (EPOR) on erythroid progenitor cells in the bone marrow, activating intracellular signaling pathways such as JAK2–STAT5, PI3K–AKT, and MAPK, which promote the survival, proliferation, and differentiation of erythroid precursor cells into mature red blood cells. In equine physiology, erythropoietin plays a crucial role in maintaining adequate oxygen delivery to tissues, which is particularly important for athletic performance and endurance in horses. Dysregulation of EPO production can contribute to anemia associated with chronic disease or kidney dysfunction. Horses are also used as comparative models for studying exercise physiology and erythropoiesis, and research on equine erythropoietin has contributed to understanding red blood cell regulation during intense exercise, hypoxia, and blood disorders, as well as the detection of recombinant EPO misuse in equine sports.