Milk thistle (MT; Silybum marianum), a member of the Asteraceae family, is a therapeutic herb with a 2,000‐year history of use. MT fruits contain a mixture of flavonolignans collectively known as silymarin, being silybin (also named silibinin) the main component. This article reviews the chemistry of MT, the pharmacokinetics and bioavailability, the pharmacologically relevant actions for liver diseases (e.g., anti‐inflammatory, immunomodulating, antifibrotic, antioxidant, and liver‐regenerating properties) as well as the clinical potential in patients with alcoholic liver disease, nonalcoholic fatty liver disease, viral hepatitis, drug‐induced liver injury, and mushroom poisoning. Overall, literature data suggest that, despite encouraging preclinical data, further well‐designed randomized clinical trials are needed to fully substantiate the real value of MT preparations in liver diseases.