A man exposed himself to a teenage girl in a skate park on the Ise Lodge estate in Kettering.
The incident happened between 8.15am and 8.45am on Monday, February 23, in the skate park area between Cheyne Walk and Grantown Close.
The offender is described as white, about 19-years-old, 5ft 7in, with a slim build and short cropped, blonde hair.
He wore a black Adidas tracksuit top and bottoms, which had three white stripes down the side of the arms and legs.
Officers are appealing for witnesses or anyone with any information about the incident to call Northamptonshire Police on 101.