The Investec Champions and Challenge Cup pool stages come to a close this weekend, with Munster and Connacht aiming to preserve their places in European competition beyond the Six Nations.
All four Irish provinces face French opposition this week, a nice appetiser for Ireland and France's Six Nations opener in Paris next month.
Leinster and Ulster are already assured of progression to the last 16 of the Champions and Challenge Cup respectively, with both sides looking for wins that will lock in home advantage for the knockout stage.
Leinster are away to Bayonne, as Leo Cullen's side look to make it a full four out of four in their pool, and secure one of the top seeds for the remainder of the competition.
Munster, meanwhile, welcome very familiar opposition to Thomond Park, for their 20th meeting with Castres. The province have to win to keep their qualification hopes alive.
Ulster are the first of the provinces in action on Saturday afternoon, hosting Stade Francais at Affidea Stadium in the Challenge Cup.
And Connacht will be hoping to secure qualification for the Round of 16 in the Challenge Cup, welcoming French strugglers Montauban to Dexcom Stadium.
RADIO
There will be live commentary of Munster v Castres from 5.30pm on RTÉ Radio 1's Saturday Sport.
TV
All Champions Cup and Challenge Cup games involving the Irish provinces will be shown live on Premier Sports.
ONLINE
We'll have live scoring, reports and reaction from all the province's games.
WEATHER
Conditions don't look great in Bayonne, where Leinster are in action on Saturday afternoon. It's likely to be around 10C, but a strong chance of rain at Stade Jean-Dauger.
Munster and Castres should have much nicer weather to play rugby in in on Saturday evening in Limerick, with a dry evening forecast at Thomond Park, gentle wind, and temperatures around 6C.
In the Challenge Cup, Ulster host Stade Francais at lunchtime on Saturday, with Belfast forecast to have some rain that morning, which may linger into the early stages of the game, while it will be around 7C.
And in Galway, it's expected to be a cold, dry, and relatively wind-free evening at Dexcom Stadium, where Connacht host Montauban.
PERMUTATIONS: WHAT'S AT STAKE FOR LEINSTER AND MUNSTER IN THE CHAMPIONS CUP?
This will be a first ever meeting of Leinster and Bayonne, although Stade Jean-Dauger will be familiar to several members of this Leinster side, who would have played for Ireland at this venue against Samoa in a World Cup warm-up game in 2023.
Leinster secured qualification for the round of 16 with their dramatic 25-24 win against La Rochelle last week, and a win for Leo Cullen's side will keep them in the hunt to secure one of the top seeds in the knockouts.
The four-time champions are yet to hit top form, but they have been putting a winning run together, with eight victories in a row since their October defeat to Munster.
Bayonne, effectively, have nothing to pay for, with the Basque side yet to pick up a point in Pool 3, and they would require an enormous win to even stand a chance of dropping through the back door and into the Challenge Cup.
Gregory Patat's side are currently mid-table in the French Top14, but are on a poor run of form, losing five of their last six games in all competitions.
Bayonne: Cheikh Tiberghien; Tom Spring, Sireli Maqala, Manu Tuilagi, Yohan Orabe; Joris Segonds, Herschel Jantjies; Ignacio Calles, Lucas Martin, Junior Tagi; Ewan Johnson, Lucas Paulos; Alexandre Fischer, Arthur Iturria (capt), Nika Lomidze.
Replacements: Facundo Bosch, Emosi Tumania, Emerick Setiano, Alvaro Garcia Iandolino, Baptiste Heguy, Manex Ariceta, Guillaume Martocq, Victor Hannoun.
Leinster: Jimmy O'Brien; Tommy O'Brien, Garry Ringrose, Robbie Henshaw, Joshua Kenny; Harry Byrne, Jamison Gibson-Park; Jack Boyle, Rónan Kelleher, Tadhg Furlong; RG Snyman; James Ryan; Max Deegan, Josh van der Flier, Caelan Doris (capt).
Replacements: Dan Sheehan, Jerry Cahir, Thomas Clarkson, Joe McCarthy, Scott Penny, Luke McGrath, Sam Prendergast, Rieko Ioane.
Referee: Luke Pearce (RFU)
The best of enemies, this will be the 20th meeting of Munster and Castres Olympique, a renewal of the most common game in Champions Cup history.
While Munster are playing their 210th game in the competition, this will be a 106th Champions Cup outing for the French side, who have now had Munster as their opposition for 18.8% of their games.
There is plenty on the line this weekend at Thomond Park, with both sides still able to secure qualification, and Munster know defeat will end their involvement in the Champions Cup early.
Castres were 16-14 winners when these sides met in France last season, although Munster still comfortably lead the head-to-head 13-5, with one draw in 2017.
The French side can qualify for the next round with a win, but they have lost on all eight previous visits to Thomond Park.
Munster: Shane Daly; Thaakir Abrahams, Tom Farrell, Alex Nankivell, Ben O'Connor; Jack Crowley, Craig Casey; Jeremy Loughman, Niall Scannell, Michael Ala’alatoa; Jean Kleyn, Fineen Wycherley; Tadhg Beirne (capt), Jack O’Donoghue, Gavin Coombes.
Replacements: Lee Barron, Michael Milne, Oli Jager, Edwin Edogbo, Brian Gleeson, Ethan Coughlan, JJ Hanrahan, Dan Kelly.
Castres: Theo Chabouni; Christian Ambadiang, Vuate Karawalevu, Jack Goodhue, Geoffrey Palis; Pierre Popelin, Jeremy Fernandez; Atunaisa Sokobale, Loris Zarantonello, Will Collier; Gauthier Maravat, Tom Staniforth; Baptiste Delaporte (capt), Baptiste Cope, Florent Vanverberghe.
Replacements: Teddy Durand-Pradere, Antoine Tichit, Aurelien Azar, Leone Nakarawa, Tyler Ardron, Santiago Arata, Enzo Herve, Atu Manu.
Referee: Matthew Carley (RFU)
While Ulster didn't get to play last week due to the cancellation of their fixture with Cheetahs in Amsterdam, the bonus-point 28-0 win they were rewarded with has guaranteed qualification to the Round of 16.
This weekend's opponents Stade Francais have also secured qualification with a game to spare, with this clash in Belfast serving as a pool decider.
Stade have been enjoying a solid season, third in the Top14 through 14 games, and with a trip to Bordeaux-Begles coming up next week, they may prioritise their domestic form, particularly with qualification secured.
The French side won this competition in 2016/17, and have been to the final on two other occasions, while this is Ulster's first time ever playing in the pool stages.
All previous 11 meetings of the side came in the Champions Cup, with Stade leading the head-to-head 6-5.
Ulster: Jacob Stockdale; Robert Baloucoune, James Hume, Stuart McCloskey, Zac Ward; Jack Murphy, Nathan Doak; Angus Bell, Tom Stewart, Tom O'Toole; Iain Henderson (capt), Harry Sheridan; Dave McCann, Nick Timoney, Bryn Ward.
Replacements: Rob Herring, Eric O'Sullivan, Scott Wilson, Matt Dalton, Sean Reffell, Conor McKee, Jake Flannery, Jude Postlethwaite.
Stade Francais: Mathis Ibo; Charles Laloi, Jeremy Ward (capt), Tani Vili, Lester Etien; Zack Henry, Paul Abadiel; Jack Iscaro, Alvaro Garcia Albo, Giorgi Melikidze; Pierre-Henri Azagoh, Jacques Botha; Juan-Martin Scelzo, Mathieu Hirigoyen, Yoan Tanga.
Replacements: Lucas Peyresblanques, Yanis Lux, Sergo Abramishvili, Setareki Turagacoke, Tanginoa Halaifonua, Thibaut Motassi, Louis Foursans-Bourdette, Samuel Ezeala.
Referee: Adam Leal (RFU)
A first ever meeting of Connacht and Montauban, and the French side will hold the distinction of being the final visitors to Dexcom Stadium, before the ribbon is cut on Connacht's new Clan Stand.
Last week's agonising collapse against Montpellier was a fourth defeat in a row for Stuart Lancaster's side, and it's been more than two years since they lost five on the spin.
Even with two defeats from three in the Challenge Cup so far, a win this weekend will guarantee their place in the Round of 16, although they could even progress with a defeat, if Black Lion fail to beat Zebre in Georgia.
Connacht have a strong record at home against French teams in the Challenge Cup.
While they lost to Racing 92 in their most recent hosting of a Top 14 side, that ended a run of 10 consecutive wins at home against the French in this competition.
Connacht: Sam Gilbert; Shane Jennings, Harry West, Cathal Forde, Finn Treacy; Jack Carty, Matthew Devine; Billy Bohan, Dave Heffernan, Sam Illo; Darragh Murray, Josh Murphy; Cian Prendergast (capt), Paul Boyle, Sean Jansen.
Replacements: Dylan Tierney-Martin, Denis Buckley, Jack Aungier, Joe Joyce, Sean O'Brien, Ben Murphy, Sean Naughton, Sean Walsh.
Montauban: Jean Seux;; Gade Asaeli, Simon Renda, Maxime Mathy, Paul Vallee; Jerome Bosviel, Hugo Zabalza; Lucas Seyrolle, Maixent da Costa, Sione Mafileo; Clement Bitz; Lewis Bean, Fred Quercy (capt), Tjuee Uanivi, Nafi Ma'afu.
Replacements: Ru-Hann Greyling, Leo Aouf, Noa Kanika, Karl Wilkins, Mael Castel, Thomas Fortunel, Gibson Popoali'i, Facundo Pomponio.
Referee: Ben Connor (WRU)
You can see the full list of fixtures, results and standings for the Champions Cup here, and the Challenge Cup here.
Listen to the RTÉ Rugby podcast on Apple Podcasts, Spotify or wherever you get your podcasts.
