All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Riding horses is one of the greatest reasons of unveiling some parts of one’s body, like legs and arms, and it is also a reason of wearing some tight clothes which shape the body, while a woman is ordered to cover all her body and she is forbidden to appear in any form which could lead to temptation. Allaah Says (what means): {… and to wrap [a portion of] their head covers over their chests and not expose their adornment [i.e. beauty] except to their husbands, their fathers, their husbands fathers, their sons, their husbands’ sons,…}{Quran 24:31]. Therefore, it is absolutely not permissible for women to ride horses in public places.
Allaah Knows best.