The victim has been taken to hospital, one man has been arrested.
Police were called by the ambulance service at 4.47am on Thursday morning to a report of a stabbing on Mill Street West, Dewsbury.
They found a man in his 20s with a stab wound to his back and lacerations to his face. He has been taken to hospital for treatment to non-life threatening injuries.
A man has been arrested on suspicion of assault and remains in police custody.
Enquiries are ongoing in the Mill Street West area to establish the circumstances and there will be an increased policing presence in the area.
Anyone with information is asked to contact police on 101, quoting crime reference 13190416321.