Officers investigating the unprovoked assault on a woman as she left Airdrie Sports Centre in North Lanarkshire on Saturday morning say the group were hanging around outside.
She suffered serious lacerations to her face and was taken for treatment to Monklands Hospital.
The five youths are described as white, between 15 and 16 years old.
One was wearing a white T-shirt and had dirty blond hair. A second was wearing yellow shorts and had brown hair.
The third youth, who has fair hair, was wearing peach-coloured shorts and the fourth was wearing a dark-coloured top.
Detective Sergeant Kenny Dalrymple said: "I am sure local people will know who these young men are and I am appealing to them to contact us."