A woman was grabbed by the wrist and punched in the face after she refused to allow a man to join her as she walked along a Northampton town centre road.
The assault happened in St Giles Street, Northampton, between 3.30am and 4.20am this morning.
A spokesman for Northamptonshire Police said: “A woman was walking along St Giles Street when a man tried to engage her in conversation.
“He asked her to join him for a walk, becoming abusive when she refused. He then grabbed her wrist and punched her, causing a black eye.”
The man is white, between 30 and 35-years-old, and wore a green T-shirt, black shorts and black socks.
Witnesses or anyone with information can call Northamptonshire Police on 101.
Alternatively, information can be given anonymously to Crimestoppers on 0800 555 111.