Alcohol is primarily metabolized in the liver. The liver contains enzymes such as alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH) that break down ethanol into acetaldehyde and then into acetate, which is further processed and eliminated from the body. Other organs like the brain, heart, and kidneys play minor roles, mostly in alcohol distribution or excretion rather than metabolism. Therefore, the correct answer is: liver.