North Wales Police said the alarm was raised at about 10:20 GMT on Tuesday on the trail between Penmaenpool, near Dolgellau, and Barmouth.
Officers said they are trying to establish the woman's identity but the death is not being treated as suspicious at the moment.
The coroner for north west Wales has been informed.
The body of a woman in her 30s has been discovered on a cycle path along the Mawddach estuary in Gwynedd.