Pelous, the 29-year-old back row forward who captained Les Bleus 15 times between 1997 and 2002, was named skipper in the 22-man France squad announced by coach Bernard Laporte.
Scrum-half Galthie was injured in France's 38-3 win over Scotland at the Stade de France on Sunday, and his replacement in the number nine shirt is expected to be Dimitri Yachvili, with the uncapped Mathieu Barrau on the bench.
The starting line-up for the Ireland game at Lansdowne Road will be announced next Tuesday at Marcoussis.
France squad to play Ireland in Dublin:
Jean-Jacques Crenca (Agen), Sylvain Marconnet (Stade FranÃƒÂ§ais), Christian Califano (Saracens), Raphael Ibanez (Castres), Jean-Baptiste Rue (Agen), Fabien Pelous (Stade Toulousain), Olivier Brouzet (Montferrand), David Auradou (Stade FranÃƒÂ§ais), Olivier Magne (Montferrand), Serge Betsen (Biarritz), Sebastien Chabal (Bourgoin), Imanol Harinordoquy (Pau), Dimitri Yachvili (Biarritz), Mathieu Barrau (Agen), Gerald Merceron (Montferrand), Francois Gelez (Agen), Damien Traille (Pau), Thomas Castaignede (Saracens), Clement Poitrenaud (Stade Toulousain), Xavier Garbajosa (Stade Toulousain), Vincent Clerc (Stade Toulousain), Aurelien Rougerie (Montferrand).