Swine interleukin-3 (IL-3) is a hematopoietic growth factor primarily produced by activated T cells and mast cells that supports the proliferation, differentiation, and survival of multipotent hematopoietic progenitors through signaling via the IL-3 receptor complex (IL-3Rα/CD123 and the common β chain), activating JAK/STAT, MAPK, and PI3K pathways. In swine health, IL-3 plays an important role in regulating myeloid cell development, including monocytes, macrophages, dendritic cells, basophils, and mast cells, thereby influencing innate immunity, inflammatory responses, and host defense against bacterial and viral infections relevant to production systems. Dysregulated IL-3 signaling may contribute to excessive inflammation, allergic-type responses, or altered immune cell dynamics during respiratory and enteric diseases that impact growth performance and herd productivity. Beyond its importance in livestock health, swine IL-3 is highly valuable in animal model research because pigs share close physiological, immunological, and hematopoietic similarities with humans, making them strong translational models for studying bone marrow biology, inflammatory disorders, sepsis, and immune cell development. As such, swine IL-3 supports both veterinary immunology applications and comparative biomedical research aimed at understanding hematopoiesis and immune regulation across species.