Police are hunting for a man who was reportedly masturbating while standing alone in a suburban Perth park wearing only a hat.

A resident opposite Luketina Reserve in Wembley Downs reported seeing the naked man on January 13 at about 10pm.

They informed police he was committing an indecent act in the middle of the park and was nude except for a hat.

The man is described as aged between 20 and 30 with fair skin and a solid build.

Scarborough Police are investigating and want to hear from anyone with information.

Call the Scarborough station on 9441 6400 or report information online.