Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size using water pressures some 75 to 500 times normal blood pressure (6 to 20 atmospheres). The balloon crushes the fatty deposits, opening up the blood vessel for improved flow, and the balloon is then deflated and withdrawn. A stent may or may not be inserted at the time of ballooning to ensure the vessel remains open.

The word is composed of the combining forms of the Greek words ἀγγεῖον angīon ‘vessel’/‘cavity’ (of the human body) and πλάσσω plasso ‘form’/‘mould’. Angioplasty has come to include all manner of vascular interventions that are typically performed in a minimally invasive or percutaneous method.

Metal stents and drug eluting stents result in an equivalent chance of death when used for primary angioplasty of ST elevation myocardial infarction.