The 23-year-old remains in hospital with serious facial injuries following the assault in Pilrig Park, Edinburgh, early on Sunday.
The woman had been out with friends at the Picture House nightclub and left around 3am, Lothian and Borders Police said. She was discovered in a play area of Pilrig Park at 6am by members of the public.
Detective Inspector Scott Cunningham said: “This has been a brutal and unprovoked attack on a lone woman as she made her way home.
“Her injuries could only have been caused through significant and violent force, and a major investigation has now been launched.”