Cardiff Blues and Ospreys will go head-to-head in a bid to secure fourth place in Conference A of Guinness PRO14, and keep their Heineken Champions Cup qualification hopes alive.
Connacht sealed the third and final spot for the PRO14 Finals Series with a 29-22 victory over Wales' Capital Region at Galway last time out.
With Ospreys clinching maximum points on their two-match tour to South Africa, Allen Clark's side currently occupy fourth place in Conference A, one point ahead of Cardiff Blues.
Principality Stadium will play host to a straight shoot-out between the Welsh rivals at Judgement Day, as the campaign reaches its climax on Saturday.
Scarlets also take on Dragons at the Welsh capital, as Wayne Pivac's men also look to advance up the Conference B table. They currently sit in fifth with 50 points, but have their sights set on fourth-placed Edinburgh (51) and Benetton (52) who take on Glasgow Warriors and Zebre on the final weekend, respectively.
The winner of Cardiff Blues v Ospreys will take on the side that finish fourth placed in Conference B in the play-off for the final place in next season's Heineken Champions Cup.
Tickets for the final day climax at Judgement Day are on sale now