The two sides' respective fortunes against England – a bonus point loss for the Irish and a win for the Welsh – so far look like they could prove decisive.
And Eddie Jones' Red Rose will also be on the prowl, hoping for any slip up from the Welsh.
But there is still hope that Joe Schmidt can win his final Six Nations as Ireland coach as they travel to Cardiff.
How can Wales win the Six Nations?
Wales simply require any win against Ireland to secure the grand slam and lift the Six Nations trophy.
Warren Gatland's men are just one point ahead of England and have a far inferior points difference, but should they beat the Irish that will be rendered irrelevant due to a three-point Grand Slam bonus.
How can England win the Six Nations?
England must first hope for a favour from Ireland at the early match in Cardiff.
Should Wales fail to beat Joe Schmidt's side, the door will open for England.
Eddie Jones would then be able to guarantee the title with a bonus point win, while even a four-point win would likely be enough barring a mathematical miracle.
How can Ireland win the Six Nations?
Ireland's fate is out of their hands, but they will have a chance of lifting the Six Nations trophy should they beat Wales in Cardiff.
Then they will have to sit back and wait to see what England do against Scotland at Twickenham.
Should they win and England fail to win, the Irish will retain their crown.
Can Ireland win the Six Nations if England beat Scotland?
Ireland can win the Six Nations if England also win, but they will require a bonus point victory in Wales while England must fail to get the extra point against Scotland.
That would mean Wales shipping four tries at home in this competition for the first time since England visited in 2001.
Should Ireland achieve a bonus point and England not, they will also have to win by a whopping 65 points more than any England victory over Scotland.
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