The victim, in her 20s, was left "fighting for her life" after the assault in Victoria Park, Leicester, at about 23:40 BST on Monday.
She was dragged into bushes and found near recycling bins about an hour later, Leicestershire Police said.
The suspect was arrested on Tuesday night and detectives have renewed their appeal for information.
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Police said the woman had been walking alone along a well-lit section of the park before she was attacked about the head and upper body.
Large parts of the public space were cordoned off on Tuesday as forensic officers combed the scene for evidence.
Det Ch Insp Rob Widdowson said: "This was a really brutal attack, the victim has been left with horrendous injuries and is fighting for her life.
"We still need to trace anyone who may have been in the area of Victoria Park [late on Monday night or early on Tuesday morning] and who may have seen something which can help us with our enquiries.
"You may not think what you saw is significant, but we still want to speak to you."
Det Supt Neil Castle added: "Whilst crossing the park she was attacked and subsequently dragged into some bushes, where she was seriously assaulted. She sustained horrific injuries."
A 17-year-old boy has been arrested on suspicion of attempted murder over a "horrific" attack on a woman in a park.