The memorial, a metal ring weighing half a ton suspended from the surrounding pines, has the names of all 69 of the people killed in the attack engraved on it.
Called Lysningen or ‘The Clearing', it has been designed by the Bergen-based architects 3RW.
“This memorial is for survivors who lost their loved ones on Utøya, but also for all other visitors,” Kolbein Fridtun, whose daughter Hanne Kristine was killed in Breivik's attack, told Norway's state broadcaster NRK.
“I get a lump in my throat when I stand here. It is perhaps not surprising, because my daughter's name is hanging here on the ring,” he said.
Fridtun has was a key member of the group of bereaved who selected the memorial from a shortlist of four.
“The other options were also very nice, but this was what we ended up with. I think we have made a good choice,” he said.
Jørgen Watne Frydnes, the general manager of Utøya, said the memorial looked better now it has been completed than he had expected from the design drawing.
“It is actually much better than I had thought,.” he said. “The frame around the woods and the silence of nature, makes it feel like a well.”
An open day is being held on July 8 for people who want to visit the island.
The memorial will officially open on July 22, the fourth anniversary of Breivik's attack, when the island will be opened for a memorial day.
Breivik attacked a Labour party youth camp on the island, mercilessly shooting dead the mainly teenaged participants, many of them with shots to the head at near point black range.
He was sentenced in 2012 to 21 years in prison, the longest sentence possible under Norwegian law.