It happened at Mojo’s Bar on Parliament Street, Harrogate in the early hours of 16 September when a group of people were fighting both inside and outside of the premises.
Officers are asking the man in the image or any members of the public who can help identify him, to get in touch as they believe he will have information that will help the investigation.
Anyone with any information is asked to call North Yorkshire Police on 101, and pass information to the Force Control Room for reference 12230175678.
If you wish to remain anonymous, you can pass information to Crimestoppers on 0800 555 111.
Please quote the reference number 12230175678 when passing on information.