The fixture dates for this season's Heineken Champions Cup and EPCR Challenge Cup have been confirmed, with Leinster and Connacht set to play at home on the weekend of 11-12 December, while Munster and Ulster are on the road.
Leinster welcome Bath to the Aviva Stadium on the Saturday for a 3.15pm kick-off, with Connacht hosting Stade Francais at 1pm a day later.
Ulster make the trip to Parc des Sports Marcel Michelin on the Saturday to face Clermont Auvergne at 6.30pm, while Munster are in action on Sunday at Coventry Building Society Arena against Wasps.
Toulouse, who completed a magnificent Champions Cup-Top 14 double last season, will kick off the defence of their European title on the Saturday against Cardiff at the Arms Park at 1pm.
The Champions Cup will be competed for by 24 clubs, including nine previous winners with as many as 38 European titles between them, in two pools of 12 over four pool stage rounds.
The eight highest-ranked clubs from each pool will qualify for the knockout stage which will consist of a round of 16 on a home and away basis, quarter-finals and semi-finals, with the final in Marseille on 28 May next year.
The clubs ranked nine to 11 in each of the pools will qualify for the Round of 16 of the Challenge Cup.
Round 1 –10/11/12 December
Round 2 – 17/18/19 December
Round 3 – 14/15/16 January 2022
Round 4 – 21/22/23 January 2022
Champions Cup Round of 16 (1st leg) & Challenge Cup Round 5 – 8/9/10 April 2022
Champions Cup Round of 16 (2nd leg) & Challenge Cup Round of 16 – 15/16/17 April 2022
Quarter-finals – 6/7/8 May 2022
Semi-finals – 13/14/15 May
Challenge Cup final – Friday 27 May 2022; Marseille
Champions Cup final – Saturday 28 May 2022; Marseille
Follow Scarlets v Munster (Sunday 2pm) via our live blog on RTÉ.ie/sport or the RTÉ News app, or watch live on RTÉ2 and RTÉ Player. Watch Leinster v Zebre (Saturday, 1pm) on RTÉ2 and RTÉ Player.