The assault happened in the Tates Avenue area of the city at around 10pm on Saturday night.
The 18-year-old victim suffered swelling to her forehead after she was punched by an unknown man.
He is described as being around 5 foot, 7 inches tall, athletic build with short black hair and swarthy skin.
He was wearing a white hooded jacket, black jeans and white trainers with red flashes.
It's understood he made off in the direction of the Lisburn Road.
Police have appealed for information.
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