Nonalcoholic fatty liver disease (NAFLD) is the most common form of liver disease in the United States, affecting up to 30% of adults. There are two forms of NAFLD: nonalcoholic fatty liver (NAFL), defined as 5% or greater hepatic steatosis without hepatocellular injury or fibrosis, and nonalcoholic steatohepatitis (NASH), defined as 5% or greater hepatic steatosis plus hepatocellular injury and inflammation, with or without fibrosis. Individuals with obesity are at highest risk of NAFLD. Other established risk factors include metabolic syndrome and type 2 diabetes mellitus. Although NAFLD is common and typically asymptomatic, screening is not currently recommended, even in high-risk patients. NAFLD should be suspected in patients with elevated liver enzymes or hepatic steatosis on abdominal imaging that are found incidentally. Once other causes, such as excessive alcohol use and hepatotoxic medications, are excluded in these patients, risk scores or elastography tests can be used to identify those who are likely to have fibrosis that will progress to cirrhosis. Liver biopsy should be considered for patients at increased risk of fibrosis and when other liver disorders cannot be excluded with noninvasive tests. Weight loss through diet and exercise is the primary treatment for NAFLD. Other treatments, such as bariatric surgery, vitamin E supplements, and pharmacologic therapy with thiazolidinediones or glucagon-like peptide-1 analogues, have shown potential benefit; however, data are limited, and these therapies are not considered routine treatments. NAFL typically follows an indolent course, whereas patients with NASH are at higher risk of death from cardiovascular disease, cancer, and end-stage liver disease.