Abstract Background: Stroke commonly affects cognition and, by definition, much vascular dementia follows stroke. However, there are fundamental limitations in our understanding of vascular cognitive impairment, restricting understanding of prevalence, trajectories, mechanisms, prevention, treatment, and patient service needs. Aims: Rates, Risks and Routes to Reduce Vascular Dementia (R4VaD) is an observational cohort study of post-stroke cognition. We aim to recruit a wide range of patients with stroke, presenting to geographically diverse UK hospitals, into a longitudinal study to determine rates of, and risk factors for, cognitive and related impairments after stroke, to assess potential mechanisms and improve prediction models. Methods: We will recruit at least 2000 patients within six weeks of stroke with or without capacity to consent, and collect baseline demographic, clinical, socioeconomic, lifestyle, cognitive, neuropsychiatric and informant data using streamlined patient centred methods appropriate to the stage after stroke. We will obtain more detailed assessments at 4-8 weeks after the baseline assessment and follow-up by phone and post yearly to at least 2 years. We will assess diagnostic neuroimaging in all, and high-sensitivity inflammatory markers, genetics, blood pressure (BP) and diffusion tensor imaging in mechanistic sub-studies. Planned Outputs: R4VaD will provide reliable data on long-term cognitive function after stroke, stratified by prior cognition, stroke- and patient-related variables, and improved risk prediction. It will create a platform enabling sharing of data, imaging and samples. Participants will be consented for re-contact, facilitating future clinical trials, and providing a resource for the stroke and dementia research communities.