The last widely-cited historical record of Scotland’s beavers, dating from 1526 to 1527, placed them around Loch Ness.
Alan McDonnell, head of nature restoration at Trees for Life, said: “The Ness Beaver Project is now set to be a major milestone for nature recovery in Britain.
“Five hundred years since Loch Ness became the last recorded site of Scotland’s beavers before they were eradicated, they are back with the space and habitat to flourish.”
He said the beavers brought “the potential for new wetlands, more wildlife, and healthier rivers.”
The beavers will dig channels, coppice trees and build dams to create pools, wetlands and light-filled woodland gaps.
It is hoped these will support frogs and dragonflies, with the abundance of insects providing food for birds and bats.
Trees For Life said that on smaller streams, beaver dams slow the flow of water and trap sediment, helping to improve water quality.