The article presents the third universal definition of myocardial infarction (MI) developed by a joint task force of the European Society of Cardiology (ESC), the American College of Cardiology Foundation (ACCF), the American Heart Association (AHA), and the World Heart Federation (WHF). The definition aims to standardize the diagnosis and classification of MI, which is a major cause of death and disability worldwide. The criteria for acute and prior MI are detailed, emphasizing the importance of cardiac biomarkers and electrocardiographic (ECG) findings. The document also covers the pathological characteristics of MI, including the detection of myocardial injury and necrosis using biomarkers and imaging techniques. It provides guidelines for the clinical classification of MI, distinguishing between spontaneous and procedure-related events, and outlines diagnostic criteria for MI associated with percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). The article highlights the role of imaging techniques such as echocardiography, radionuclide imaging, magnetic resonance imaging (MRI), and computed tomography (CT) in diagnosing and characterizing MI. Additionally, it discusses the challenges and considerations in diagnosing MI, particularly in the presence of non-ischaemic conditions and in patients with renal failure or heart failure. The document emphasizes the need for precise and consistent definitions to improve the understanding and management of MI.The article presents the third universal definition of myocardial infarction (MI) developed by a joint task force of the European Society of Cardiology (ESC), the American College of Cardiology Foundation (ACCF), the American Heart Association (AHA), and the World Heart Federation (WHF). The definition aims to standardize the diagnosis and classification of MI, which is a major cause of death and disability worldwide. The criteria for acute and prior MI are detailed, emphasizing the importance of cardiac biomarkers and electrocardiographic (ECG) findings. The document also covers the pathological characteristics of MI, including the detection of myocardial injury and necrosis using biomarkers and imaging techniques. It provides guidelines for the clinical classification of MI, distinguishing between spontaneous and procedure-related events, and outlines diagnostic criteria for MI associated with percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). The article highlights the role of imaging techniques such as echocardiography, radionuclide imaging, magnetic resonance imaging (MRI), and computed tomography (CT) in diagnosing and characterizing MI. Additionally, it discusses the challenges and considerations in diagnosing MI, particularly in the presence of non-ischaemic conditions and in patients with renal failure or heart failure. The document emphasizes the need for precise and consistent definitions to improve the understanding and management of MI.