Human Interleukin-11 (IL-11) is a multifunctional cytokine belonging to the IL-6 family—which includes IL-6, IL-11, IL-27, IL-31, leukemia inhibitory factor (LIF), oncostatin M (OSM), ciliary neurotrophic factor (CNTF), cardiotrophin-1 (CT-1), and cardiotrophin-like cytokine factor 1 (CLCF1)—all of which signal through receptor complexes containing the shared gp130 subunit. IL-11 binds to its specific receptor IL-11Rα, forming a complex with gp130 that activates JAK/STAT3 and MAPK signaling pathways to regulate gene expression. In humans, IL-11 plays important roles in hematopoiesis, particularly in promoting megakaryocyte maturation and platelet production, as well as in mucosal protection, epithelial regeneration, reproductive biology, and modulation of inflammatory responses. Clinically, recombinant human IL-11 (oprelvekin) has been used to treat chemotherapy-induced thrombocytopenia. However, dysregulated IL-11 signaling has been increasingly implicated in fibrotic diseases (including cardiac, pulmonary, and hepatic fibrosis), gastrointestinal inflammation, and tumor progression, where IL-11–driven STAT3 activation can promote stromal remodeling and cancer cell survival. As both a therapeutic agent and emerging therapeutic target, human IL-11 is central to research on hematologic support, fibrosis biology, inflammatory disease, and oncogenic signaling pathways.