Police want to find Andrew McNair, 24, of Willow Hey, Skelmersdale, after a woman was attacked in the town in December.
The victim suffered a injured jaw and damaged teeth during the assault.
McNair is described as white, 6ft 4in tall, with ginger hair, brown eyes and tattoos on his arm and neck. He speaks with a Liverpool accent.
He has links to the Liverpool and West Lancashire areas and officers are urging the public not to approach him.
Det Sgt Steve Ollerton, of Lancashire Police said: “We are appealing for information leading to the arrest of Andrew McNair who is wanted in connection with a serious assault in Skelmersdale in December.
“McNair has been wanted for several weeks now and it is vital we find him as soon as possible.
“Anyone with information is urged not to approach him but instead contact police immediately.
“If you can help, please call us on 101 quoting crime reference SB1605233.”
Alternatively independent charity Crimestoppers can be contacted anonymously on 0800 555 111 or online at Crimestoppers-uk.org.