Atenolol is a selective β₁ receptor antagonist, a drug belonging to the group of beta blockers (sometimes written β-blockers), a class of drugs used primarily in cardiovascular diseases. Introduced in 1976, atenolol was developed as a replacement for propranolol in the treatment of hypertension. The chemical works by slowing down the heart and reducing its workload. Unlike propranolol, atenolol does not pass through the blood–brain barrier thus avoiding various central nervous system side effects.

Atenolol is one of the most widely used β-blockers in the United Kingdom and was once the first-line treatment for hypertension. The role for β-blockers in hypertension was downgraded in June 2006 in the United Kingdom to fourth-line, as they perform less appropriately or effectively than newer drugs, particularly in the elderly. Some evidence suggests that even in normal doses the most frequently used β-blockers carry an unacceptable risk of provoking type 2 diabetes.

Atenolol is used for a number of conditions including: hypertension, angina, acute myocardial infarction, supraventricular tachycardia, ventricular tachycardia, and the symptoms of alcohol withdrawal.