Police are appealing for witnesses after a serious assault on Queen Street which happened around 2.30am on Sunday when a man approached a 33-year-old woman and engaged her in conversation.
A 34-year-old man whom she was previously then joined them, and an altercation took place between the two men.
Two men, who are believed to have known the suspect, have then approached the group and attempted to calm the situation.
The woman’s companion was then assaulted and sustained a serious facial injury. He was taken to Edinburgh Royal Infirmary.
The suspect and two men were last seen heading down Queen Street Gardens East.
The suspect is described as white, 5ft 11inches tall, aged 20-30, with a stocky build and a local accent. He had short fair hair and stubble. He was possibly wearing a grey-coloured jumper with thin black stripes.
One of the men who intervened is described as white, 6ft 2inches tall, in his early 30s, with a slight build. He had short ginger hair and was clean-shaven. He was wearing a white t-shirt and dark trousers.
The second man is described as white, 5ft 8inches tall, in his early 30s, with a slight build. He had short dark hair and stubble on his face. He was wearing a grey-hooded jacket and dark jeans.
Detective Constable Alison Wyllie said: “This was a violent attack which has left the victim requiring ongoing treatment, and we’re conducting extensive enquiries in order to trace the suspect.
“I would ask anyone who may have seen the assault, or recognises the description of the suspect or the two witnesses, to get in touch.”
Anyone with information is asked to contact Police Scotland on 101 or contact Crimestoppers anonymously on 0800 555 111.