<p>Metabolic-dysfunction-associated steatotic liver disease (MASLD, previously known as non-alcoholic fatty liver disease or NAFLD) is a prevalent and heterogeneous condition affecting nearly 30% of the global population. MASLD is defined as excessive hepatic lipid accumulation with at least one feature of insulin resistance, with potential progression to metabolic dysfunction-associated steatohepatitis, cirrhosis and hepatocellular carcinoma. The disease often coexists with insulin resistance and cardiovascular and chronic kidney diseases. Human genetics has shed light on MASLD predisposition and its causal association with type 2 diabetes and insulin resistance, enabling the field to progress towards precision-medicine therapeutics. Convergent selection of somatic mutations in genes involved in glucose and lipid metabolism in cirrhotic livers suggests adaptive responses to gluco-lipotoxicity that influence end-stage liver disease. Recently, two distinct types of MASLD, with specific clinical trajectories, were identified on the basis of partitioned polygenic risk scores. Future studies are needed to integrate this knowledge, enabling earlier detection, risk stratification and targeted therapies.</p>