It will be home to millions of birds, mammals, wild plants and insects.
The Ł8.5million scheme is the brainchild of the Woodland Trust, which is creating the forest on farmland and ancient woodland at Sandridge, near St Albans, Hertfordshire.
Land near Sandridge in Hertfordshire, where the trust is planning to create England's largest new native forest with the planting of 600,000 trees
'A continuous new native forest of this size has never been created in England before,' said chief executive Sue Holden.
'We have been searching for some time for a major site to buy in the South East.
'Our plans for the new forest at Sandridge are historic in scale and offer an unmissable opportunity to plant such a huge number of trees and benefit so many people.
The Ł8.5million project covering 850 acres in Hertfordshire will be bigger than the post-2012 Olympic Urban Park in London.
'Native woodland is our equivalent of the rainforest. Woods and trees are not only good for the soul, they are life-enhancing and make a big difference to people's health and well-being.
'We estimate that two million people live within 15 miles of Sandridge.
'Our new wood will provide a large and accessible space for people at a time when there is huge pressure to develop and build on land in the South East.
The trust said the project would rival Sherwood-the forest in Nottinghamshire associated with the legend of Robin Hood-which is just over 1,000 acres.
Although there are larger woods in England, the charity believes its project, at twice the size of Regent's Park in London, will be the biggest continuous block of forest to be planted from scratch.
The first trees may be planted as early as this winter on the land, which at the moment is mostly farmland with pockets of traditional woodland.
The trust said the new forest would be open to the public and provide 'health, education and leisure benefits'.
Miss Holden said: 'Woodland establishes very quickly. Within two years, a tree will be twice the size of the child who planted it.
'Within 12 years, we see a wonderful young forest taking shape.'
England has lost half its ancient woodland since the 1930s, with most being felled to make way for houses, farming or conifer plantations.
Today just five per cent of England is covered in native woods-making the country one of the least-wooded in Europe.
Conifer plantations offer little for wildlife. Plants and animals thrive when woods contain a mixture of species and ages of tree.
They also need areas of dead and fallen timber, clearings where saplings are growing, and gradual borders between woods and open countryside.
The new woodland will be planted with four species - field maple, oak, ash and hornbeam - over the next five years.
The Woodland Trust hopes that wild flowers - including bluebells - will start growing on the forest floor within a decade.
The new greenery should attract dozens of species of mammal - including badgers, pygmy shrews, pipistrelle bats - and butterflies such as the white admiral,wall brown and silverwash fritillary.
Other species that could benefit include slow worms, great crested newts, spotted fly catchers, nightingales, cuckoos, woodpeckers and tree sparrows.
 Sherwood Forest has been reduced to a fraction of its former size.
During the time associated with Robin Hood, about 1200AD, it is thought to have stretched for 100,000 acres.
Pollen records show there has been an unbroken woodland cover there for at least 10,000 years.
More than 900 trees in the forest are 600 years old or more.
http://www.dailymail.co.uk/news/article-1039292/Massive-new-8-5-million-woodland-create-largest-continuous-native-forest-seen-England.html