|RBS Six Nations - the opening weekend|
|Friday, 6 February: Wales v England (Cardiff, kick-off 20:05 GMT)|
|Saturday, 7 February: Italy v Ireland (Rome, 14:30 GMT)|
|Saturday, 7 February: France v Scotland (Paris, 17:00 GMT)|
|Click here for coverage details: Six Nations on the BBC|
The 2015 Six Nations will kick off at the Millennium Stadium with the roof firmly open on Friday night as Wales and England do battle once again.
It will be the first in a series of mouth-watering match-ups as holders Ireland, who dramatically clinched the title last year on points difference from England, look to retain their crown.
The women's tournament promises to be equally entertaining. England line up as world champions, eager to claim the Six Nations title back from France, who won last year.
Both the English and Irish men's sides are without several players due to injury, but this has opened the door to new talent as well as crowd-pleasers like Danny Cipriani and Nick Easter.
This year's tournament also carries more weight than just national pride, with all six teams using it as a test for the World Cup in September.
BBC Sport casts an eye over where the crucial battles will be fought and who and what to look out for over the next six weeks...
Who starts as favourites?
Champions Ireland will have eyes on repeating the achievements of the class of 2014. But a resurgent Wales will fancy their chances of winning back the championship they snatched from the grasp of England the year before.
For England, 2015 is a huge year in prospect with the role of hosting the World Cup to follow later in the year. But coach Stuart Lancaster will be forced to field a side missing numerous first choice players for the opening fixture at the Millennium Stadium.
Across the Channel, France will point to an impressive set of results against teams from the Southern Hemisphere last autumn as a reason to fancy their chances.
A new-look Scotland under Vern Cotter won a number of plaudits for their performance against New Zealand in November and would have every right to argue they will be a force at home.
"Vern Cotter's a breath of fresh air for Scotland rugby and this team will be better prepared than ever for the challenge ahead," said BBC Radio 5 live commentator Ian Robertson.
For Italy, they will hope three games in Rome will give them a chance to upset the favourites and throw a spanner into the works, rather than the typical wooden spoon.
Former Ireland and British Lions hooker Keith Wood says: "Ireland are the holders and are title contenders again this year - my only fears are complacency and our ever-increasing injury list."
Wales captain Sam Warburton is happy to be labelled favourites by some.
"I'd rather be favourites than underdogs," he said.
"You work hard to try and get to number one, to try to be the best team, so when you do get given that [favourites tag] that's something I do quite enjoy."
More than just a tale of the roof
The 2015 championship begins with a encounter that has a guaranteed electric atmosphere on a Friday night at a packed Millennium Stadium.
Two years ago, England's Grand Slam hopes were destroyed by a rampant Wales.
Fast forward to the present day and the talk is about having the stadium roof open rather than closed, and the Welsh roar, that's dominated much of the pre-match analysis.
England have prepared for the vocal chorus of more than 70,000 spectators by training in front of loud speakers to replicate the wall of noise.
But England assistant coach Mike Catt insists the side will not be fazed by the occasion.
"I wouldn't say it's intimidating. Only six or seven of our players haven't been to the Millennium Stadium and played in front of that sort of crowd," said Catt.
Former England coach Sir Clive Woodward remembers the ferocious atmosphere of that night in 2013.
"I didn't think a crowd could influence a game until then," he said.
"That blinking Welsh anthem started and the English didn't look confident and I said to Jiffy [Jonathan Davies] I've never heard anything like that in my life.
"Something amazing happened that night."
Faces to look out for - old and new
This year's championship will be without some big names, either enforced through injury like England fly-half Owen Farrell or because of retirement in the shape of Ireland's talisman Brian O'Driscoll.
But, some old faces will be returning. England number eight Nick Easter returns for the first time since 2011 and will look to nurture George Ford through his first chance to establish himself as first choice fly-half.
O'Driscoll's retirement means Johnny Sexton will take centre stage for Ireland.
The fly-half is not available for the start of the tournament because of concussion but has become a very strong leader in the Irish set-up and is very assertive on the international stage.
Meanwhile, former Wales fly-half and BBC pundit Jonathan Davies likes the look of Scotland centre Alex Dunbar and France winger Teddy Thomas as players to make an impact.
"With Dunbar, Scotland have missed a direct, creative footballer in the centres and a combination of him and winger Tommy Seymour should score tries," he said.
"Teddy Thomas could set things alight for France."
Italy captain and number eight Sergio Parisse will lead the Azzurri, with Newcastle lock Josh Furno, 25, among those looking to inspire Jacques Brunel's side to an upset.
A women's championship to savour
In the women's Six Nations, the championship will boast a world champion side in England.
But the side which begins its tournament against Wales on Sunday will be a markedly different one from that which won the World Cup in August.
Coach Gary Street has departed just two weeks before the tournament, while captain Katy McLean will be absent from selection as she joins a sevens squad with an eye on the Rio Olympics.
Tamara Taylor takes the captain's armband in her place.
BBC Sport's Sara Orchard believes England will brush off those pre-tournament distractions and take the title ahead of 2014 Grand Slam champions France.
Follow it all across the BBC
BBC Sport will have comprehensive coverage of the Six Nations on television, radio, online and social media.
You'll be able to follow every kick, pass, scrum, ruck and maul from the first to the final whistle.
As well as live matches, there will also be on-demand highlights online and on the BBC Sport app on selected Connected TVs, mobiles and tablets.
There will also be live text commentary on every match on the BBC Sport website.
A new addition this year will be Six Nations Rewind, featuring classic matches from the championship every match weekend on BBC Two.
Can't catch the games live? Have no fear, a 10-minute catch-up service will be available to download on BBC iPlayer and will bring you right up to date with the latest action.