A man was taken to hospital with serious facial injuries after an attack at a new bar in Holmfirth.
Officers were called to Victoria Square at about 2am on Saturday by the ambulance service after a 21-year-old man was found there with head injuries.
He was taken to hospital before police discovered he was the victim of an assault at the Ten Fourteen bar on Dunford Road.
The man suffered serious but not life-threatening facial injuries.
Kirklees CID is investigating.
DI Andrew Lockwood of Kirklees CID said: “We are investigating the circumstances of this incident and would like to speak with anyone was present in the Ten Fourteen bar who witnessed a fight there which took place between around 12.30am and 2am.
“Anyone who witnessed the incident in the Ten Fourteen bar is asked to contact Kirklees CID on 101 referencing police crime number 13190562865."
Information can also be given online at www.westyorkshire.police.uk/101livechat or anonymously to the independent Crimestoppers charity on 0800 555 111