A Twitter account about Saudi prisoners of conscience said Ahmed al-Amari died in Jeddah on Sunday, Arabi21 website reported.
Amari was arrested and jailed in August 2018 after publishing a book featuring recommendations to Saudi rulers.
He was reported on January 13 to have suffered a brain hemorrhage after prison officials failed to provide him with needed medical care.
He was taken to a hospital in Jeddah after going into a comma in his cell and died on Sunday.