Just after 9 p.m. Saturday, Madera Police responded to the Fresno River Trail near Riverview Drive and Westberry Boulevard.
Investigators say a man pepper sprayed a woman who was walking in the area and was not letting her leave.
The woman was able to escape.
Police are now searching for the suspect described as a man with thick curly hair, wearing a green flannel long sleeve and blue jeans.
He also has a noticeable limp and may be riding or pushing a bicycle.
If you see someone that matches that description call Madera Police.