Defending champions Ireland will fight to set the standard again, while England will be desperate to atone for last year's fifth-place finish.
Here, Press Association Sport looks at five players to watch ahead of another compelling Six Nations championship.
Billy Vunipola, England
The one man more than any other – including Manu Tuilagi – who can transform England's phase play. Boss Eddie Jones loves deploying number eight Vunipola in midfield given his wide-ranging skill-set: from crashing over the top to passing out to the back field, Vunipola sucks in defenders through both power and guile. Three arm fractures have limited the Saracens wrecking ball to just four caps since 2016. England will desperately hope that rotten injury luck is a thing of the past, with Jones' men itching to lay down an early marker in World Cup year.
James Ryan, Ireland
The Leinster lock's consistent excellence binds the packs at both province and country, and all at the tender age of 22. Ryan's unerring accuracy is a dream come true for Test boss Joe Schmidt, whose blueprint is based entirely around attention to detail. Schmidt demands his players trust the structure, and when men like Ryan do just that Ireland trend towards success. Ultra-reliable in both lineout and scrum, Ryan produces tackle and carry counts to satisfy most back-rowers. A massive asset for the defending champions.
Aaron Wainwright, Wales
Dragons flanker Wainwright enjoyed a whirlwind 2018, leading to his first three Test caps and a key part in Wales' 20-11 victory over South Africa in November. The 21-year-old has still only been playing rugby for less than four years, but can already be viewed as an important part of Warren Gatland's set-up. Wainwright's form has been so strong in fact that he could well already be commanding a starting berth even if Wales had all their back-rowers fit. His emergence can offset a clutch of loose forward injuries then, and boost Wales' pack.
Finn Russell, Scotland
Livewire fly-half Russell mirrors head coach Gregor Townsend's outlook with his front-foot mindset. Former Scotland and British and Irish Lions playmaker Townsend could hardly ask for an on-field general more honed in his attacking image. Russell's move to Paris big guns Racing 92 will only embolden the talented ball-player yet further, and that will certainly benefit the neutrals. Scotland's biggest challenge will be keeping him fresh all the way to the World Cup, given the heavy demands on blue-chip recruits in France's gruelling Top 14.
Romain Ntamack, France
Not satisfied with the burden of his famous name, this rookie 19-year-old will be charged with leading France's backline, as and when his Test debut comes. The son of ex-Les Bleus wing Emile, Ntamack has already helped France to the 2018 World Rugby Under-20 Championship crown. Regular action at top club Toulouse has now also propelled him to Jacques Brunel's 31-man squad. The time to justify the hype and expectation appears nigh.
