Nitroglycerin, also known as glyceryl trinitrate (GTN), is a medication used for heart failure, high blood pressure, anal fissures, painful periods, and to treat and prevent chest pain caused by decreased blood flow to the heart (angina) or due to the recreational use of cocaine. This includes chest pain from a heart attack. It is taken by mouth, under the tongue, applied to the skin, or by injection into a vein.

Common side effects include headache and low blood pressure. The low blood pressure can be severe. It is unclear if use in pregnancy is safe for the baby. It should not be used together with medications within the PDE5 inhibitor family such as sildenafil due to the risk of low blood pressure. Nitroglycerin is in the nitrate family of medications. While it is not entirely clear how it works, it is believed to function by dilating blood vessels.

Nitroglycerin was written about as early as 1846 and came into medical use in 1878. It is on the World Health Organization's List of Essential Medicines. The drug nitroglycerin (GTN) is a dilute form of the same chemical used as the explosive, nitroglycerin. Dilution makes it non-explosive. In 2020, it was the 165th most commonly prescribed medication in the United States, with more than 3 million prescriptions.