On 26th November 2020, the World Health Organization (WHO) launched their guidelines on physical activity and sedentary behaviour. This Special Collection curated by the Cochrane Campbell Global Ageing Partnership includes associated relevant topics addressing healthy ageing, aligning with the concerted global action of the Decade of Healthy Ageing (2021 to 2030). This Special Collection brings together a selection of Cochrane Reviews assessing the benefits of physical activity interventions on activity levels, physical function, and symptoms. The reviews synthesize evidence regarding the general population, or groups of people who have specific health conditions.