It's round one of the Investec Champions Cup as Connacht, Ulster, Munster and Leinster begin their European adventures.
Can Leo Cullen's four-time champions get over the line again after narrow losses to La Rochelle in the last two finals? The rivals face off on Sunday.
Munster, winners in 2006 and 2008, are the URC champions and will aim to bring back the glory days of Europe once more. They welcome debutants Bayonne to Thomond Park on Saturday.
Ulster, the 1999 champions, are in action earlier on the same day, with Bath the hosts at The Rec.
Connacht are the first Irish side in action as they welcome Bordeaux to The Sportsground this evening.
Here's all you need to know about round one.
ONLINE
We'll have live blogs, live scoring, reports and reaction across the weekend.
TV
Munster v Bayonne is live on RTÉ2 and RTÉ Player on Saturday, with coverage getting under way at 16.45pm. Connacht v Bordeaux, Bath v Ulster and La Rochelle v Leinster are on TNT.
RADIO
There will be live commentary of Munster v Bayonne on Saturday Sport on RTÉ Radio 1.
WEATHER
Galway is in for wet and windy conditions all Friday but there may be some respite as the forecast is for the rain to stop ahead of the 8pm kick-off. Temperatures around 10C.
More pleasant conditions are forecast for Bath for Saturday afternoon, sunny and around 11C.
Slightly cooler in Limerick on Saturday afternoon at 8C with light rain showers predicted.
La Rochelle is set for cloudy and increasingly windy conditions in about 15C.
Connacht kickstart the Irish European adventure as they welcome Bordeaux-Begles to The Sportsground.
Pete Wilkins' side have fallen off the pace in the URC after winning their opening three matches and are looking to avoid a third straight loss in all competitions.
The Westerners are back in the elite competition having reached the last 16 of the Challenge Cup last season where they lost to Benetton.
They make five changes to the side that lost to Leinster last weekend with Bundee Aki making his first appearance of the season.
Bordeaux, under head coach Yannick Bru, are seventh in the Top14.
Last season they lost all four of their Champions Cup ties but have named a strong outfit for the game in Galway, including France internationals Matthieu Jalibert, Maxime Lucu and Damian Penaud.
Connacht: Mack Hansen; Byron Ralston, Cathal Forde, Bundee Aki, Andrew Smith; JJ Hanrahan, Caolin Blade; Denis Buckley, Dave Heffernan, Finlay Bealham; Darragh Murray, Joe Joyce; Cian Prendergast, Shamus Hurley-Langton, Seán Jansen.
Replacements: Tadhg McElroy, Peter Dooley, Jack Aungier, Niall Murray, Conor Oliver, Michael McDonald, David Hawkshaw, John Porch.
Bordeaux-Begles: Romain Buros; Damian Penaud, Nicolas Depoortere, Ben Tapuai, Pablo Uberti; Matthieu Jalibert, Maxime Lucu; Ugo Boniface, Clement Maynadier, Sipili Falatea; Guido Petti, Thomas Jolmes; Pierre Bochaton, Pete Samu, Tevita Tatafu.
Replacements: Maxime Lamothe, Ben Tameifuna, Carlu Sadie, Alexandre Ricard, Bastien Vergnes-Taillefer, Antoine Miguel, Paul Abadie, Nans Ducuing.
Referee: Karl Dickson (Eng)
Ulster, who suffered a disappointing home loss to Edinburgh last weekend, travel to Bath for their opening tie.
Their form has been patchy and they sit in seventh place in the URC table after four wins and three losses.
Last season they lost to Leinster in the last 16. Rob Herring, Jake Flannery and Mike Lowry return to the squad, following their injuries.
Bath, under former Munster head coach Johann van Graan, are in second place in the Premiership.
They lost three and drew one of their four Challenge Cup matches last season. Finn Russell starts for the hosts.
Bath: Matt Gallagher; Joe Cokanasiga, Ollie Lawrence, Cameron Redpath, Will Muir; Finn Russell, Ben Spencer (capt); Beno Obano, Tom Dunn, Will Stuart; Elliott Stooke, Charlie Ewels; Miles Reid, Sam Underhill, Alfie Barbeary
Replacements: Niall Annett, Juan Schoeman, Thomas du Toit, GJ van Velze, Jaco Coetzee, Louis Schreuder, Orlando Bailey, Will Butt.
Ulster: Stewart Moore; Rob Baloucoune, James Hume, Stuart McCloskey, Jacob Stockdale; Billy Burns, Nathan Doak; Steven Kitshoff, Tom Stewart, Tom O'Toole; Alan O’Connor, Iain Henderson (capt); Dave Ewers, Nick Timoney, James McNabney.
Replacements: Rob Herring, Andrew Warwick, Marty Moore, Kieran Treadwell, Matty Rea, John Cooney, Jake Flannery, Mike Lowry.
Referee: Pierre Brousset (Fra)
Two-time winners Munster host tournament debutants Bayonne in Limerick on Saturday evening.
Graham Rowntree's side come in off the back of a 40-29 victory over Glasgow, which sees them into fourth in the URC standings.
Recently retired Ireland and Munster backs Keith Earls and Andrew Conway will be honoured at half-time.
Edwin Edogbo, Diarmuid Barron, Shane Daly, Oli Jager, Simon Zebo and Patrick Campbell have all been ruled out with minor injuries.
Gregory Patat's Bayonne have won all four Top14 home games but have lost all five on the road and sit in tenth place.
Scrum-half Maxime Machenaud is named to start, while 63-cap Wallabies centre Reece Hodge is on the roster but a foot injury means he's still waiting on his debut for the Basque side.
Munster: Calvin Nash; Shay McCarthy, Alex Nankivell, Rory Scannell, Seán O'Brien; Jack Crowley, Conor Murray; Jeremy Loughman, Scott Buckley, John Ryan; Fineen Wycherley, Tadhg Beirne (capt); Tom Ahern, John Hodnett, Gavin Coombes.
Replacements: Eoghan Clarke, Josh Wycherley, Stephen Archer, Jack O'Donoghue, Alex Kendellen, Craig Casey, Tony Butler, Ben O’Connor.
Bayonne: Cheikh Tiberghien; Bastien Pourailly, Peyo Muscarditz, Riko Buliruarua, Rémy Baget; Thomas Dolhagaray, Maxime Machenaud; Matis Perchaud, Facundo Bosch, Tevita Tatafu; Denis Marchois, Kote Mikautadze; Pierre Huguet, Baptiste Heguy, Rodrigo Bruni.
Replacements: Thomas Acquier, Swan Cormenier, Junior Tagi, Arthur Iturria, Rémi Bourdeau, Gela Aprasidze, Arnaud Erbinartegaray, Tom Spring.
Referee: Luke Pearce (Eng)
Leinster's latest European odyssey begins at the home of their nemesis, La Rochelle.
It’s a repeat of the last two finals, which both ended in one-score wins for the Ronan O’Gara’s side.
Leo Cullen’s men lead the way in the URC after winning six of their opening seven matches.
Harry Byrne continues in the 10 shirt, getting the nod over Ciarán Frawley who is held back in reserve, while Tadhg Furlong is not in the squad.
Both sides will be expected to progress from the pool stages but Leinster will be desperate to avoid a fourth straight loss to the Top14 side.
O’Gara, whose side have won four and lost five league games this season, will be missing from the sideline as he serves a ban.
The Cork man has picked a strong side for the clash with Jonathan Danty, Antoine Hastoy and Will Skelton among the starting XV.
La Rochelle: Brice Dulin; Dillyn Leyds, Ulupano Seuteni, Jonathan Danty, Jules Favre; Antoine Hastoy, Tawerra Kerr-Barlow; Reda Wardi, Pierre Bourgarit (capt), Uini Atonio, Thomas Lavault; Will Skelton, Paul Boudehent, Levani Botia, Yoan Tanga.
Replacements: Sacha Idoumi, Joel Sclavi, Georges-Henri Colombe Reazel, Ultan Dillane, Rémi Picquette, Judicaël Cancoriet, Teddy Iribaren, Hugo Reus.
Leinster: Hugo Keenan; Jordan Larmour, Garry Ringrose (co-capt), Robbie Henshaw, Jimmy O'Brien; Harry Byrne, Jamison Gibson-Park; Andrew Porter, Dan Sheehan, Michael Ala'alatoa; Joe McCarthy, James Ryan (co-capt); Ryan Baird, Will Connors, Caelan Doris.
Replacements: Rónan Kelleher, Cian Healy, Thomas Clarkson, Jason Jenkins, Josh van der Flier, Ben Murphy, Ciarán Frawley, Charlie Ngatai.
Referee: Matthew Carley (Eng)
Donal Lenihan and Bernard Jackman preview the Champions Cup on Against the Head
