Thousands of Tyrone fans have travelled to Croke Park for Sunday's All-Ireland SFC final clash with Dublin.
The Red Hands are appearing in their first final for 10 years and are aiming to stop Dublin winning a fourth final in a row.
Dublin are favourites and beat Tyrone by 12 points in the 2017 semi-final.
Sinn Féin president Mary Lou McDonald, a Dublin supporter, and vice-president Michelle O'Neill, a Tyrone fan, are among those cheering the sides on.
Tyrone's underdog status has been summed by Bernard Flynn, a two-time All-Ireland winner with Meath, who told Irish national broadcaster RTÉ it would be "the greatest of miracles" if they defeat Dublin.
Northern Ireland secretary of state Karen Bradley joined Taoiseach Leo Varadkar at the match.
Fans of both sides have descended on Dublin for the clash. Throw in took place at 15:30 local time.
Strabane's famous 'Tinnies' sculpture has been decked out in Tyrone colours to mark the occasion.
Tyrone have won the All-Ireland SFC three times, most recently in 2008.
Manager Mickey Harte was in charge for Tyrone's previous All-Ireland successes.
He is still the manager , but only one player from Tyrone's All-Ireland winning side remains - Colm Cavanagh.
Meanwhile Dublin are the second-most successful county in the competition's history with 28 titles.
Victory on Sunday would give them four titles in a row for the first time ever - a feat previously managed by just two counties, Kerry and Wexford.
The game is expected to be played in almost perfect conditions. If it ends in a draw the replay is pencilled in for Saturday 15 September.