The victim has reported that she was walking to school when an unknown man hit her to the face.
The incident took place at around 8.30am on Friday, September 29 in a lane behind Palace Avenue.
The man has been described as aged around 17 or 18 and wearing a blue baseball cap and brown jacket.
Anyone who witnessed the incident, or with information that could identify the offender, is asked to contact Llanelli Police on 101 quoting incident number 51 of September 29. If you are Deaf, hard of hearing or speech impaired text the non-emergency number on 07811 311 908.