Those who walk two or more hours a week – or who reach walking speeds of three miles an hour or faster – have a lower risk than women who do not walk, the study found.
Walking briskly lowers the risk by 37 per cent, while two or more hours of walking a week cuts the risk by 30 per cent.
This applied for any type of stroke, whether clot-related (ischaemic) or bleed related (haemorrhagic).
When each type was analysed separately, the experts found brisk walking cut the risk of haemorrhagic stroke by 68 per cent, while two or more hours a week of walking cut the risk by 57 per cent.
Brisk walking cut the risk of ischaemic stroke by 25 per cent, while two hours or more a week led to a 21 per cent lower risk.
The research, on more than 39,000 women with an average age of 54, was published in the Journal of the American Heart Association (JAMA).
Lead author, Jacob Sattelmair, from the Harvard School of Public Health in Boston, Massachusetts, said: "Physical activity, including regular walking, is an important modifiable behaviour for stroke prevention.
"Physical activity is essential to promoting cardiovascular health and reducing risk of cardiovascular disease, and walking is one way of achieving physical activity."
Dr Peter Coleman, from the Stroke Association, said: "Regular exercise is an easy way to help reduce your risk of stroke and walking is one way to do this."