Ireland are vying to become the first team to win three successive Six Nations titles but they face a daunting start to life without Paul O'Connell.
Joe Schmidt's side host Wales on the opening weekend before trips to France and England. They have a poor record against the latter in post-World Cup years, losing heavily in 2008 and 2012.
Peter O'Mahony and Iain Henderson miss the entire tournament through injury and Ireland also have concerns in the front row. Marty Moore is ruled out with a hamstring tear, while Mike Ross and Cian Healy have not played since December.
Head coach: Joe Schmidt
Captain: Rory Best
Last year: Winners
Strengths: Ireland are not short of options in the back row or at centre, with the inclusions of uncapped duo CJ Stander and Stuart McCloskey increasing competition for places, while Sean O'Brien, Jared Payne and Robbie Henshaw have hit the ground running on their returns from injury. That trio are important components in a defensive system that has conceded just seven tries in the last two championships.
Weaknesses: There is a Paul O'Connell-sized hole that requires filling in the second row and that is compounded by the absence of O'Mahony and Henderson. We have already mentioned Ireland's problems at tighthead and there are also concerns over the form and fitness of Johnny Sexton. The poor performances of the provinces in the Champions Cup has extended Ireland's World Cup hangover.
Who we will love: Stuart McCloskey has been in fantastic form for Ulster and looks more than capable of making the step up to the international stage. The 23-year-old beat 26 defenders in five Champions Cup matches and combines raw power with excellent footwork and hands.
Who will split opinion: Rob Kearney has been a consistent starter for Ireland but his place at full-back is being put under intense pressure by Payne, who has caught the eye in the No 15 shirt for Ulster since returning from injury.
MVP: Rory Best is a popular choice as captain and the Ulsterman will lead by example with his scrummaging and work at the breakdown. He was one of Ireland's best performers at the World Cup and could win his 100th cap later this year.
The big debate: Will Ireland persist with their kick-chase strategy that has served them well in the Six Nations or will Schmidt mix things up? Four years out from a World Cup, now would be the best time to experiment with a more expansive game plan.