Orange Order grand master Edward Stevenson used the platform at Rossnowlagh's Twelfth to assure brethren in the Republic that no one will be building a Trump-esque "wall around Donegal" when Brexit happens.
Speaking as over 50 bands marched through the seaside village on the edge of the Atlantic, he paid tribute to the "perseverance and faithfulness" of the Donegal lodges and reassured them that they will remain good neighbours.
He said more consideration would be given to how to "recognise and support" the Protestant minority community in the Republic and that, despite a neutral stance on Brexit, they were now committed to see it take place.
"That does not mean that the United Kingdom and Ireland cannot be good neighbours, or indeed become better neighbours," he said.
"We have many ties which bind us together, not least our kith and kin in the Orange community.
"No one wants to see a return to heightened security along the border or any hindrance to the large amount of cross-border trade which flows daily between the jurisdictions.
"As a west Tyrone dairy farmer, I know fully the importance of cross-border agricultural processing facilities. I have no doubt that, whatever the final political and economic agreement, despite President Trump's remarks while visiting a few weeks ago, no one wants to build a wall around Donegal."
In June Mr Trump had compared the post-Brexit Irish border to his own efforts to build a wall along the US border with Mexico.
The US President had been speaking to Taoiseach Leo Varadkar when he made a series of remarks about "your wall, your border". Mr Varadkar had immediately responded by saying: "The thing we want to avoid, of course, is a border wall."
Speaking after the Rossnowlagh speeches, Ulster Unionist councillor Derek Hussey said: "Brexit will make no difference to the Orange family in Ireland.
"It makes no difference to the Orange family worldwide.
"There are Orangemen in New Zealand, Australia, Canada and the US, Scotland, England and Wales.
"Borders don't count in the Orange Order."
Rossnowlagh is the only major march to take place in the Republic.
The Twelfth in Donegal has been held in the village since the 1900s, and has taken place every year since 1978.