Dublin City Council has begun proceedings to put a compulsory purchase order (CPO) on the park in Dartmouth Square, Ranelagh.
The park, in the middle of the south Dublin square, came to public attention last month when residents discovered that the "public" park was privately owned and the gates were padlocked shut.
They protested that they had been locked out by an Athlone man claiming to own the park, Noel O'Gara, who is involved in a granite and marble business.
The residents had assumed the park was owned by Dublin City Council. The first they knew of a new owner was when the four gates leading to the park were clamped shut. Last week, they unlocked the gates and reopened the park.
Mr O'Gara, of Ballinahowen, Athlone, claims he owns the freehold title and the council has been negotiating with him to secure the park's future.
The green space was originally laid out by the Darley estate when Dartmouth Square was being developed in the 1880s.
In a statement yesterday Dublin City Council said at no stage did the estate own the park in its entirety.
The council's lease had expired in 1997.
The statement said it had received a letter from solicitors for Marble and Granite Tiles Ltd and Mr O'Gara said the company would retain possession until such time as the council negotiated a new lease.
"The council has now decided to initiate compulsory purchase order proceedings to acquire the entire property," the council's statement said.
The move has been welcomed by Mary Freehill, city councillor and former lord mayor. She has asked the city council to check on the titles of all the public space in its charge.
"Because land has become so valuable, Dubliners are at risk of being robbed of their public spaces," she said.