The Ulster GAA released 125 balloons today to mark its foundation.
Clubs across Ulster have been asked to fly special flags next month to highlight the anniversary.
President Tom Daly and 10 children from St Malachy's Primary School in Armagh released the black and amber balloons.
"One hundred and twenty five years ago on the 1st November the GAA was founded by a group of visionary men in Thurles. Today we celebrate that day and celebrate the many successes of the Association since that date.
"The GAA has grown and developed into one of the greatest sporting organisations in the world and we are all proud to be part of that."
He said they remembered all volunteer members who worked tirelessly to build Ireland's largest sporting, cultural and community movement.
"This is a special time to celebrate the successes of our Association as well as remembering all of those volunteer members who worked tirelessly to build Ireland's largest sporting, cultural and community movement," he added.
A large crowd of supporters gathered for the celebrations including Social Development Minister Margaret Ritchie, Regional Development Minister Conor Murphy, Mayor of Armagh Thomas O'Hanlon, and Church of Ireland Dean at St Patrick's Cathedral in Armagh Patrick Rooke.