Natural killer T cells are innate-like and tissue-resident lymphocytes,which recognize lipid antigens and are enriched in the liver.Natural killer T cells play important roles in infections,tumors,autoimmune diseases,and metabolic diseases.In this study,we summarize recent findings on biology of natural killer T cells and their roles in hepatitis B virus and hepatitis C virus infection,autoimmune liver diseases,alcoholic liver disease,nonalcoholic fatty liver disease,and hepatocellular carcinoma.Controversial results from previous studies are discussed,and indicate the dynamic alteration in the role of natural killer T cells during the progression of liver diseases,which might be caused by changes in natural killer T subsets,factors skewing cytokine responses,and intercellular crosstalk between natural killer T cells and CDld-expressing cells or bystander cells.