A 24-year-old man is in critical but stable condition in Wellington Hospital after he was found bleeding on the street.
Police say the French national was found semi-conscious near the corner of Durham St and Aro St at about 2am on Saturday.
Police do not know how the man, who has serious head and arm injuries, came to be injured.
They say he was in Courtenay Place on Friday night with friends, but became separated from them about midnight.
He has dark hair and was wearing dark jeans, a dark top, a brown leather jacket and glasses.