Chronic inflammation occurs when the acute inflammatory response fails to resolve, driven by persistent infection, autoimmune reactions, or prolonged exposure to irritants. Unlike acute inflammation (neutrophil-mediated, resolves in days), chronic inflammation is characterized by simultaneous tissue destruction and repair involving macrophages, lymphocytes, and fibroblasts. Activated M1 macrophages release pro-inflammatory cytokines (TNF-α, IL-1, IL-6), reactive oxygen species, and matrix metalloproteinases that cause ongoing tissue damage. Fibroblasts deposit collagen, leading to fibrosis and organ dysfunction. Chronic inflammation underlies atherosclerosis, type 2 diabetes, cancer, and autoimmune diseases.