Frailty is common in stroke and has important disease- and treatment-modifying effects. The need to develop clinical practice and research for the impact of frailty on stroke is likely to increase in the coming decades as the global population ages, resulting in a higher burden of frailty that is likely to be borne disproportionately by lower- and middle-income countries. The global nature of frailty in stroke necessitates global action. This World Stroke Organization Scientific Statement synthesizes the current evidence relating to the prevalence and effects of frailty across the stroke pathway. Furthermore, it includes expert consensus on priority areas from a global panel: standardization of frailty assessments for research, explicit measurements of frailty (in addition to disability) in large clinical trials, dedicated studies investigating the treatment-modifying effects of frailty in acute stroke and secondary prevention, research investigating the impact of frailty on the different aspects of recovery and rehabilitation after stroke, and understanding the mechanisms underpinning the relationship between frailty and stroke for potential therapeutic exploitation. This scientific statement has been reviewed and approved by the World Stroke Organization Executive.