A woman suffered a broken jaw when a stranger punched her in the face outside a kebab shop in Brighton.
She was trying to stop two men from attacking her boyfriend.
Sussex Police urged the good Samaritan who gave her first aid to come forward.
The attack happened outside City Kebabs in London Road, Brighton, between 3am and 4am on Sunday 19 September.
The woman, 20, and her 19-year-old boyfriend were walking by when two men, one sat on a motorbike, yelled abuse at the couple.
The men then approached the victim’s boyfriend and when the woman stepped out in front him she was punched in the face.
She was taken to the Royal Sussex County Hospital in Eastern Road, Brighton, for treatment.
Her boyfriend was uninjured.
One of the suspects was described as white, in his late teens to early 20s, 5ft 11in tall, of average build and with short dark hair.
The second was said to be a similar age, 5ft 9in tall, with longer hair and wearing jeans and a t-shirt.
Both ran off north up London Road.
Anyone with information is asked to contact Sussex Police on 0845 6070999 or to call the independent charity Crimestoppers anonymously on 0800 555111.