<p>Ischemia results from an inadequate supply of oxygen and nutrients to tissues, often due to obstruction of arterial blood flow. Reperfusion refers to the restoration of blood flow to tissues after the obstruction is removed. Severe clinical conditions such as myocardial infarction, cerebral ischemia, stroke, and hemorrhagic shock can lead to ischemia/reperfusion (I/R) injury. During this process, oxidative stress triggers various biological events, including inflammation, mitochondrial dysfunction, endoplasmic reticulum stress (ERS), and apoptosis, all of which impair critical physiological functions. The presence of hyperglycemia exacerbates these pathophysiological processes, further intensifying I/R injury. Hyperglycemia contributes to increased oxidative stress, activation of inflammatory pathways, mitochondrial dysfunction, and elevated ERS. In this review, we provide a comprehensive overview of the pathophysiological mechanisms underlying I/R injury, with a particular emphasis on the role of hyperglycemia. Although numerous clinical, basic, in vivo, and in vitro studies have been conducted on this topic, further research is necessary to fully understand how hyperglycemia influences I/R injury.</p>