Hosts England have been drawn with Wales and Australia in the pool stages of the 2015 World Cup.
Scotland are in Pool B, which includes South Africa and Samoa, while Ireland's opponents in Pool D include France and Italy.
Holders New Zealand are in Group C, alongside the likes of Argentina and Tonga.
The tournament kicks off on 18 September 2015, with the final to be held at Twickenham on 31 October.
"It could have been easier, couldn't it? As they were seeded in the third tier, whichever group Wales landed in was going to make it harder, and it certainly makes things harder for England and Australia. But it is three years away and what is happening now won't necessarily affect what is going to happen in 2015. There's no need to panic or worry. Let's not forget England will be at home, and they are a difficult side to beat at home."
England were in the second tier of seeds after dropping to fifth in the world rankings and head coach Stuart Lancaster said their draw was "definitely a pretty tough pool".
"Once we knew there was a chance of us being drawn against Wales, I guess it was fate - it was always going to happen wasn't it?" he told BBC Radio 5 live.
"To win the World Cup you have to win big games and I have a huge amount of respect for what Wales have done recently. We know their squad pretty well, it is a young side and a lot of them will still be around in 2015.
"Australia have just beaten us
and if you look at the age and profile of their squad, they have got some young lads as well. We will look forward to it."
England have played Australia five times in previous World Cups, winning three times -
famously in the 2003 final in Sydney
- and losing twice, including the 1991 final at Twickenham.
Wales and England have met twice in the competition, both times in the quarter-finals. The Welsh won 16-3 in the first World Cup in 1987 with England winning 28-17 on their way to lifting the trophy nine years ago.
Wales were World Cup semi-finalists last year but, after defeats by Argentina, Samoa, New Zealand and Australia, the Six Nations champions have dropped to ninth in the world rankings, resulting in them being drawn in a tough pool as they were only in the third tier of seeds.
2015 World Cup pools
- Pool A:
Oceania 1, play-off winner
- Pool B:
South Africa, Samoa,
Asia 1, Americas 2
- Pool C:
New Zealand, Argentina, Tonga, Europe 1, Africa 1
- Pool D:
Italy, Americas 1, Europe 2
Winner Pool B v Runner-up Pool A; Winner Pool C v Runner-up Pool D; Winner Pool A v Runner-up Pool B; Winner Pool D v Runner-up Pool C
They have a poor record against Australia having won only one out of their five World Cup encounters, beating the southern hemisphere side 22-21 in the third-fourth place play-off in the first World Cup back in 1987.
"It's a really interesting pool," said Wales captain Sam Warburton. "We have made it tough work for ourselves being seeded in the third tier having lost the last seven games.
"It was always going to be a tough pool whichever way it worked out but the fact that we have got the hosts does make it very exciting. Wales against England games have a lot of rivalry anyway and, if you throw a Rugby World Cup in the mix, then it makes it very exciting."
The winner of England and Wales' pool will play the runner-up in Pool B, featuring South Africa, Samoa and Scotland, with the runners-up facing the winner of Scotland's pool.
Scotland's recent struggles have seen them suffer autumn losses to the All Blacks, South Africa and Tonga,
which led to the resignation of Andy Robinson as coach.
They are now ranked only 12th in the world - in the third band of seeds for the tournament - and they face a tough group that includes two-time world champions the Springboks and the notoriously hard-hitting Samoa.
"It is a tough draw for Wales, but after they dropped out of the top eight, it was always going to happen. I don't think Australia and England will be too chuffed with Wales being in their group. Of the three teams though, England will be happier because to play the other teams at home is a huge advantage at a World Cup."
"My first thought was that it was going to be incredibly physical but it is a challenge and one that we are looking forward to," said Scotland captain Kelly Brown.
"As a side, we're really here to make Scotland proud and that is always our aim.
"Lately, we've not been doing that but it's up to us as a squad to really work hard over the next three years and make our nation proud."
The biggest challenge facing Ireland is France, who they are yet to beat in the World Cup. The Irish suffered heavy defeats to Les Blues at the quarter-final stage in both 1995 and 2003, and also lost 25-3 in a group game in 2007.
Ireland captain Brian O'Driscoll said: "You are always going to have teams that are capable of beating you but equally there are teams in our pool that we are capable of beating on our day.
"It's just a matter of getting consistent for four games and getting into the knock-out stage."
Ireland will have every incentive to finish top of Pool C, with New Zealand - who
beat France 8-7 in the final
on home soil in 2011 - likely to top Pool D and be awaiting the runners-up in Ireland's group in the quarter-finals.
The eight remaining places for 2015 will be filled by qualifiers, with the pools expected to be finalised by the end of 2014.