The move follows consultations with the Orange Order and will help to secure access to the 1690 site for visitors.
The Taoiseach, Bertie Ahern, said last night: "The Battle of the Boyne was one of the most important events in our island's history and indeed had a wider European significance. It should be remembered and understood by us all."
The purchase is being presented by Dublin as a contribution towards reconciliation between different traditions in a week when devolution and other key elements of the Good Friday Agreement were formally implemented.
The purchase will see the 502-acre Old Ridge Estate near Donore on the banks of the Boyne and several smaller packets of land becoming public property.
The land purchase, pioneered by the Irish Foreign Minister, David Andrews, will see an initial Irpounds 150,000 (pounds 120,000) spent on improving access and visitor facilities and information material.
An inter-departmental group in Dublin is preparing long-term plans for the site in conjunction with Louth and Meath county councils.
Mr Ahern promised the development would occur "in a way which fully reflects its huge historical importance for all of the people of the island, and in particular of course for the Unionist tradition".
This is hoped to be more suitable than an American multi-millionaire's 1986 proposal for a Boyne folk village, with a statue of Hibernia and a Dutch windmill from which battle sounds would be played over loudspeakers; or the 1990 plan by a cement firm to blast much of it for a quarry.Reuse content