Nationalists in Northern Ireland have voted to oppose Brexit, Gerry Adams said.
With the prospect of a hard land border dividing the island of Ireland, the Sinn Féin president said the Stormont Assembly poll was a mandate for Northern Ireland to receive special designated status within the EU.
Mr Adams said it was the only way to prevent a land frontier between a European state, the Republic of Ireland, and the British state in Northern Ireland.
Sinn Féin is on course to become the largest party in nationalism in the next Assembly if the power-sharing institutions can be resurrected.
Mr Adams said: "It is also a re-assertion of our position on Brexit, that this part of Ireland should have a special designated status.
"Whatever your position is on the constitutional issue, that the only way to stop a land frontier between a European state and the British state on this island is to make sure there is a special designated status within the European Union for this part of Ireland."
Northern Ireland voted remain in the June EU poll by 56% to 44%.
However some largely unionist areas voted leave and the DUP, the largest party, campaigned for Brexit.
There are concerns among some businesses that the move will damage the economy of Northern Ireland, with pharmaceuticals moving to the Republic of Ireland, even though proponents point to benefits like freedom from EU regulation.
The border at present is porous and invisible, with people and goods passing freely back and forth.
The British Government has said it wants to create a frictionless frontier post-Brexit.
Mr Adams said it was a vote of confidence in his party's position.
"It is a vote for Irish unity, a vote for us together as a people.
"As Ian Paisley famously told Martin McGuinness, we don't need Englishmen to govern us."
He said it was about agreements which had already been made being implemented as well as a little bit of manners, respect and treating others the way you would want to be treated by unionists.
Mr Adams said: "It is a vote and a mandate, and it will have to be respected by the other parties and the two governments, for a step-change, for an end to the old status quo, for a new beginning to how we do our business."
He said it was a huge vote of thanks to Martin McGuinness, whose resignation as deputy first minister in January prompted the collapse of power-sharing.