Feline Interleukin-10 (IL-10) is a potent anti-inflammatory cytokine produced primarily by regulatory T cells (Tregs), Th2 cells, macrophages, dendritic cells, and certain B-cell subsets in cats (Felis catus), where it plays a central role in limiting excessive immune activation and maintaining immune homeostasis. IL-10 signals through the IL-10 receptor complex (IL-10R1/IL-10R2), activating JAK/STAT3 pathways that suppress pro-inflammatory cytokine production (including IL-1β, TNF-α, and IL-6), inhibit antigen presentation, and downregulate Th1-type immune responses. In feline health, IL-10 is critically involved in modulating immune responses during chronic viral infections such as feline immunodeficiency virus (FIV), feline leukemia virus (FeLV), and feline infectious peritonitis (FIP), where elevated IL-10 expression can contribute to immune suppression and viral persistence. IL-10 is also associated with chronic inflammatory conditions such as gingivostomatitis and inflammatory bowel disease, where it may play dual roles in controlling inflammation while potentially limiting effective pathogen clearance. As both a biomarker of immune regulation and a functional mediator of anti-inflammatory pathways, feline IL-10 is important in vaccine studies, immunopathogenesis research, and therapeutic modulation of immune responses. In translational research, cats serve as valuable natural models for human retroviral infection (FIV as a model for HIV), coronavirus-associated immunopathology (FIP), and chronic inflammatory diseases, and characterization of feline IL-10 supports comparative studies of immune regulation, tolerance, and cytokine network balance relevant to both veterinary and human medicine.