There are two changes to the side that defeated Edinburgh in the Guinness PRO14 last time out as Joey Carbery and CJ Stander are both included.
Mike Haley starts at full-back with free-scoring Andrew Conway and Keith Earls completing the back three.
Rory Scannell and Chris Farrell continue their centre partnership with Conor Murray and Carbery paired together in the red of Munster for the first time in the half-backs.
The tight five are unchanged with Dave Kilcoyne, Niall Scannell and John Ryan in the front row with Tadhg Beirne and Billy Holland in the engine room.
Peter O’Mahony captains the side from the back row with Chris Cloete and the returning Stander completing the side.
Jeremy Loughman, Ciaran Parker and Fineen Wycherley are in line to make their Champions Cup debuts off the bench.
Munster: Mike Haley; Andrew Conway, Chris Farrell, Rory Scannell, Keith Earls; Joey Carbery, Conor Murray; Dave Kilcoyne, Niall Scannell, John Ryan; Tadhg Beirne, Billy Holland; Peter O’Mahony (C), Chris Cloete, CJ Stander.
Replacements: Kevin O’Byrne, Jeremy Loughman, Ciaran Parker, Fineen Wycherley, Arno Botha, Alby Mathewson, JJ Hanrahan, Sammy Arnold.
Man of the Match JJ Hanrahan celebrates scoring his try.
Munster moved back to the top of Champions Cup Pool 2 thanks to a vital victory over French champions Castres Olympique at a blustery Thomond Park on Sunday afternoon.
Man of the Match JJ Hanrahan, one of two late additions, was a try-scorer and kicked 100% off the tee with three conversions and three penalties as Rory Scannell and CJ Stander also touched down.
Munster face Castres in the return fixture next Saturday with two Champions Cup games in January – Munster travel to Gloucester on Friday, January 11, before Exeter Chiefs visit Thomond Park on Saturday, January 19 (5.30pm). Buy tickets here.
Two late Munster changes saw Hanrahan and Sammy Arnold replace late withdrawals Joey Carbery and Chris Farrell.
Munster started well and led 3-0 after seven minutes thanks to a straightforward Hanrahan penalty after early pressure.
Castres, playing with the wind in the first half, had presented Munster with the opportunity after a clearance kick from near their 22 bounced dead.
The Munster scrum was good, CJ Stander made a customary charge and Munster went through the phases before eventually forcing the penalty with Hanrahan making no mistake.
The out-half doubled the Munster lead after 20 minutes with the hosts in complete control. A scrum penalty inside the Castres 22 gave Hanrahan his second chance and he made it 6-0.
Munster were over for the first try on 43 minutes with Scannell darting over. Conor Murray provided the assist with the scrum-half showing great strength to hold off lock Thibault Lassalle after picking up off the base of the scrum before passing inside for Scannell to score.
Hanrahan superbly kicked the conversion and Munster led 13-0.
Castres had a chance to get off the mark on 50 minutes when their pack won a scrum penalty but Benjamin Urdapilleta was off the mark.
Unfortunately for Munster, Murray spilled the kick as he looked to collect it in the in-goal area and Castres had another opportunity with a five-yard scrum but magnificent Munster defence kept the clean sheet.
Munster were back on the front foot immediately and Hanrahan kicked his third penalty on 57 minutes to keep the scoreboard ticking over after another spell of pressure to make it 16-0.
Stander was over for Munster’s second try after 67 minutes following a sublime break and pass from Murray with the no.8 finishing powerfully. Hanarahan was on target again and Munster led 23-0.
Hanrahan scored Munster’s third try after a brilliant move started by replacement hooker Kevin O’Byrne at scrum-half with Scannell and Sammy Arnold combining with a brilliant one-two before Alby Mathewson popped the final pass for Hanrahan to finish and convert.
Andrew Conway was sin-binned late on for an early tackle as Castres looked to hit back and the visitors had the last say with Martin Laveau diving over in the right corner.
Champions Cup Round 3 Round-Up
JJ Hanrahan scored 20 points in a Man of the Match performance.
Jeremy Loughman, Ciaran Parker and Fineen Wycherley made their Champions Cup debuts off the bench.
Munster: Mike Haley (Tyler Bleyendaal, 76); Andrew Conway, Sammy Arnold, Rory Scannell (Jaco Taute, 76), Keith Earls; JJ Hanrahan, Conor Murray (Alby Mathewson, 69); Dave Kilcoyne (Jeremy Loughman, 72), Niall Scannell (Kevin O’Byrne, 45), John Ryan (Ciaran Parker, 76); Tadhg Beirne, Billy Holland (Fineen Wycherley, 69); Peter O’Mahony (C), Chris Cloete (Arno Botha, 64), CJ Stander.
Castres Olympique: Scott Spedding; Armand Batlle, Thomas Combezou, Floran Vialelle, Taylor Paris; Benjamin Urdapilleta, Ludovic Radosavljevic; Antoine Tichit, Jody Jenneker, Daniel Kotze; Loic Jacquet, Thibault Lassalle; Mathieu Babillot (C), Alex Tulou, Kevin Gimeno.
Replacements: Kevin Firmin, Paea Fa’anunu, Marc Clerc, Christophe Samson, Yannick Caballero, Julien Caminati, Martin Laveau, Rory Kockott.