David Kearney will line out on the right wing after scoring a brace of tries last time out in the league against the Cardiff Blues. He forms a speedy back-three unit with Fionn Carr and Luke Fitzgerald.
Eoin Reddan and Ian Madigan link up at half-back, while up front Cian Healy starts in the front row alongside fellow Ireland players Sean Cronin and Mike Ross. Experienced flanker Shane Jennings leads the side.
Monday's festive clash will be a sell-out and there will be no tickets available to purchase on the day.
LEINSTER (v Ulster): Luke Fitzgerald; David Kearney, Fergus McFadden, Gordon D'Arcy, Fionn Carr; Ian Madigan, Eoin Reddan; Cian Healy, Sean Cronin, Mike Ross, Damian Browne, Devin Toner, Kevin McLaughlin, Shane Jennings (capt), Leo Auva'a.
Replacements: Richardt Strauss, Jack McGrath, Jamie Hagan, Steven Sykes, Rhys Ruddock, Isaac Boss, Eoin O'Malley, Andrew Conway.