Project Abstract After the initial stages of COVID-19, a substantial proportion of patients are left with long-lasting cognitive symptoms that they continue to report months later, sometimes referred to as ‘long-haul’ patients. These long-lasting cognitive disruptions can occur even in patients with only moderate initial illness. The most commonly reported symptom is persistent fatigue, which significantly impairs daily function and quality of life. While fatigue in a subset of patients is explained by lasting cardiovascular or lung damage, many patients with no systemic issues present severe fatigue, suggesting an illness of neural origin. However, the neural basis of post-COVID fatigue is not yet known. With millions of COVID-19 cases to date, hundreds of thousands of people are expected to suffer from persistent fatigue, and identifying the neurophysiological factors underlying post-COVID fatigue is critical in order to develop an understanding of this condition and identify potential treatment routes. Given the prevalence and major impact of these symptoms on daily function in these long- haul patients, we aim to investigate the neural basis of post-COVID fatigue. We will use high spatial resolution 7T fMRI to test whether patients with persistent fatigue after COVID-19 exhibit neurovascular functional disruption. We will examine both whether spatially diffuse neurovascular impairment occurs, or focal disruption specific to subcortical arousal regulatory circuits. This project will provide a unique, high-resolution, and comprehensive assessment of neurovascular physiology in patients experiencing persistent fatigue after COVID-19.