Pyruvate kinase is a key regulator in hepatic glucose metabolism, encoded by the gene pyruvate kinase liver/red blood cells (PKLR). Systems biology-based approaches, including metabolic and gene co-expression networks analyses, as well as genome-wide association studies (GWAS), have led to the identification of PKLR as a pivotal gene influencing liver metabolism in patients with metabolic dysfunction-associated steatotic liver disease (MASLD) and hepatocellular carcinoma (HCC). Here, we review the critical role of PKLR in MASLD and HCC progression and examine the effects of PKLR modulation both in vitro and in vivo. We also discuss the development of therapeutic strategies for patients with MASLD and HCC by modulating PKLR, highlighting its promising future in a broader range of liver diseases.