Horgan continues in the back-three alongside Luke Fitzgerald and Isa Nacewa, who both started last weekend's 26-16 victory over the Newport Gwent Dragons.
Gordon D'Arcy partners Brian O'Driscoll at centre with Isaac Boss, a try scorer in Newport, and Jonathan Sexton partnering each other once again at half-back.
In all, there are six Ireland internationals in the starting pack. Props Cian Healy and Mike Ross resume in the front row and Sean O'Brien and Jamie Heaslip rejoin Kevin McLaughlin in the back row.
Leo Cullen leads the team and partners Scotland's Nathan Hines in the second row.
Internationals Heinke van der Merwe, Stan Wright, Devin Toner, Rhys Ruddock, Eoin Reddan and Fergus McFadden have been named on a strong replacements bench.
LEINSTER (v Munster): Isa Nacewa; Shane Horgan, Brian O'Driscoll, Gordon D'Arcy, Luke Fitzgerald; Jonathan Sexton, Isaac Boss; Cian Healy, Richardt Strauss, Mike Ross, Leo Cullen (capt), Nathan Hines, Kevin McLaughlin, Sean O'Brien, Jamie Heaslip.
Replacements: Aaron Dundon, Heinke van der Merwe, Stan Wright, Devin Toner, Rhys Ruddock, Eoin Reddan, Ian Madigan, Fergus McFadden.