Dear colleagues, This Special Issue, "Endothelial Dysfunction: From Pathophysiology to Novel Therapeutic Approaches", focuses on the pathophysiology of endothelial dysfunction, new biomarkers for endothelial dysfunction related to cardiovascular disorders or tumors, and novel therapeutic approaches for endothelial dysfunctions. Vascular endothelium is an active tissue and plays a crucial role in the maintenance of vascular homeostasis. Chronic exposure to risk factors, such as hypertension, high cholesterolemia, or oxidative stress, induces endothelial dysfunctions and results in a loss of endothelial integrity, smooth muscle cell proliferation, and macrophage recruitment. The pathophysiology of endothelial dysfunction (ED) is complex and multi-factorial factors are involved, such as oxidative stress or chronic inflammation. The primary prevention of cardiovascular risk factors and endothelial dysfunctions, as well as the early detection of or molecular imaging techniques for endothelial dysfunction, helps to prevent the development of cardiovascular disorders. Novel therapeutic approaches or drug delivery systems for endothelial dysfunctions have had promising beneficial effects in preclinical or clinical levels by affecting the progression of atherosclerotic changes, tumor angiogenesis, and host-immune reactions near tumor environments.