A 21-year-old woman was pulled to the floor and kicked in the face by another woman outside a pub in Stony Stratford in the early hours of Sunday morning.
Thames Valley Police is appealing for information following the assault outside the Foresters Arms pub in Wolverton Road at around 2.20am.
During the incident, the victim was pulled to the floor and received a kick to her face. This left her with severe bruising under her right eye and noticeable swelling and grazes.
Other people involved also sustained minor injuries.
The offender was a white female aged around 21 and 5ft 6ins tall. She had brown shoulder-length hair and was wearing a black and white dress.
It is believed the same offender may also have been involved in an altercation inside the pub.
Anyone with information is asked to contact PC Natasha Medlin from Milton Keynes Police Station on 101.