A 19-year-old woman suffered a swollen face, a cut lip and two broken teeth when she was punched in the face by an unknown man outside an Essex nightclub.
The woman was near CM20 on Post Office Walk, Harlow, at about 0230 BST on Saturday when she has was approached by a man.
When she turned to face him he punched her before apologising and running off.
He is described as white, aged in his 30s, around 6ft tall (1.83m), of stocky build, with balding hair and stubble.
The man had previously been shouting at a woman he called Natalie, police said.
Anyone with information is asked to contact officers.