Cardiac magnetic resonance (CMR) is a valuable tool for assessing myocardial fibrosis in various cardiomyopathies. Myocardial fibrosis, characterized by increased collagen volume fraction, impairs cardiac function and is linked to adverse cardiovascular outcomes. CMR can uniquely characterize the extent of replacement fibrosis and has prognostic value in cardiomyopathies. Myocardial T₁ mapping enhances CMR's diagnostic accuracy, especially for interstitial diffuse fibrosis. CMR can be integrated into monitoring and treatment of many patients. This review summarizes CMR's advantages and limitations in assessing myocardial fibrosis. Myocardial fibrosis is a common feature in cardiomyopathies, with different subtypes including reactive interstitial fibrosis, infiltrative interstitial fibrosis, and replacement fibrosis. Reactive fibrosis is associated with hypertension and diabetes, while infiltrative fibrosis involves amyloidosis or Fabry disease. Replacement fibrosis occurs after cell damage and is linked to various conditions. CMR techniques like late gadolinium enhancement (LGE) and T₁ mapping are used to detect and quantify fibrosis. LGE provides qualitative assessment of replacement fibrosis, while T₁ mapping offers quantitative data on fibrosis extent and composition. LGE has shown clinical utility in assessing infarct size and predicting outcomes in ischemic cardiomyopathy. However, its accuracy for absolute quantification is limited. T₁ mapping provides more precise measurements of myocardial tissue composition, including diffuse interstitial fibrosis. T₁ mapping is sensitive to various factors, including contrast agent properties and patient-specific variables, requiring standardized protocols for reliable results. Equilibrium contrast CMR is a new method that improves T₁ mapping by accounting for confounding factors. Other non-invasive methods, such as positron emission tomography and serum biomarkers, are used to assess myocardial fibrosis but are not the focus of this review. CMR, particularly with T₁ mapping, offers a promising approach for accurate and reproducible assessment of myocardial fibrosis. Future studies aim to standardize CMR techniques and improve their clinical application in various cardiomyopathies. CMR has the potential to enhance therapeutic strategies by providing detailed information on myocardial tissue composition and fibrosis extent.Cardiac magnetic resonance (CMR) is a valuable tool for assessing myocardial fibrosis in various cardiomyopathies. Myocardial fibrosis, characterized by increased collagen volume fraction, impairs cardiac function and is linked to adverse cardiovascular outcomes. CMR can uniquely characterize the extent of replacement fibrosis and has prognostic value in cardiomyopathies. Myocardial T₁ mapping enhances CMR's diagnostic accuracy, especially for interstitial diffuse fibrosis. CMR can be integrated into monitoring and treatment of many patients. This review summarizes CMR's advantages and limitations in assessing myocardial fibrosis. Myocardial fibrosis is a common feature in cardiomyopathies, with different subtypes including reactive interstitial fibrosis, infiltrative interstitial fibrosis, and replacement fibrosis. Reactive fibrosis is associated with hypertension and diabetes, while infiltrative fibrosis involves amyloidosis or Fabry disease. Replacement fibrosis occurs after cell damage and is linked to various conditions. CMR techniques like late gadolinium enhancement (LGE) and T₁ mapping are used to detect and quantify fibrosis. LGE provides qualitative assessment of replacement fibrosis, while T₁ mapping offers quantitative data on fibrosis extent and composition. LGE has shown clinical utility in assessing infarct size and predicting outcomes in ischemic cardiomyopathy. However, its accuracy for absolute quantification is limited. T₁ mapping provides more precise measurements of myocardial tissue composition, including diffuse interstitial fibrosis. T₁ mapping is sensitive to various factors, including contrast agent properties and patient-specific variables, requiring standardized protocols for reliable results. Equilibrium contrast CMR is a new method that improves T₁ mapping by accounting for confounding factors. Other non-invasive methods, such as positron emission tomography and serum biomarkers, are used to assess myocardial fibrosis but are not the focus of this review. CMR, particularly with T₁ mapping, offers a promising approach for accurate and reproducible assessment of myocardial fibrosis. Future studies aim to standardize CMR techniques and improve their clinical application in various cardiomyopathies. CMR has the potential to enhance therapeutic strategies by providing detailed information on myocardial tissue composition and fibrosis extent.