The 38-year-old was attacked after leaving Airdrie Sports Centre, North Lanarkshire, at around 10am on Saturday while walking down Waverley Drive.
She suffered serious lacerations to her face and was taken to Monklands Hospital. She was treated and released.
Officers are reviewing CCTV images.
The five youths are described as white and around 15 and 16 years old.
Enquiries show that the youths were hanging around the Sports Centre.
Detective Sergeant Kenny Dalrymple said: "This assault was entirely unprovoked and has left a woman with serious facial injuries.
"I am sure local people will know who these young men are and I am appealing to them to contact us."