West Yorkshire Police today revealed details of the attack as they appealed for witnesses.
The incident happened in the early hours of Saturday, December 9.
A spokesman said: "The victim, a 23-year-old male, was walking with a friend along Cross Church Street in Huddersfield town centre and subjected to an unprovoked assault.
"He was punched in the face, resulting in a broken jaw, and was taken to hospital for treatment."
The attacker is described as a white man, aged around 19 or 20, 5ft 10in and slim build, with mousy brown/brown hair. He was clean shaven with no visible tattoos.
Anyone with any information or who witnessed the assault is asked to contact Kirklees CID via 101, quoting crime reference 13170575209.