The event will be hosted by the RFU and Wales is the only nation outside England where matches will be played.
Details of the schedule of matches to be played at the Millennium Stadium in Cardiff will be confirmed when the full tournament structure is announced in due course.
The decision to confirm games will be played in Wales has been welcomed by the WRU Chairman David Pickering and the Group Chief Executive, Roger Lewis.
David Pickering, who is also a Wales representative on the IRB Council and executive board, said: “I am delighted for Wales and for Welsh rugby that this decision has now been confirmed.
“I want to thank my colleagues on the IRB Council and the RFU for recognising the benefit of playing games across the border in Wales.
“I’m also grateful for the support of the Welsh Government and First Minister Carwyn Jones who we’ve consulted on this matter.”
“Cardiff is extremely accessible by road, rail and air while the city centre location of the Millennium Stadium is now firmly established as a huge benefit for visiting fans.
“Our proximity to the west of England and London means the Millennium Stadium makes enormous sense as a venue for these important fixtures.
“The Rugby World Cup is now one of the greatest tournaments on the sporting calendar and Wales can be proud to be playing a pivotal role in its delivery.
“Our history as a proud rugby nation is well known and I am so pleased that thousands of Welsh rugby fans will now be able to claim real involvement in this great competition.
“Wales now has a seat on the top table of world rugby and we play a huge role in sustaining and developing the sport around the globe.
“2015 is going to be a fantastic year for rugby and, yet again, Wales will feature prominently in an epic occasion for our sport.”
WRU Group Chief Executive Roger Lewis, said: “This is a great honour for Welsh rugby and I know the staff at the Millennium Stadium will ensure the event is a huge success.
“This announcement is true confirmation of our status as worthy hosts of some of the most iconic events staged in Europe.
“We have just hosted a sensational Heineken Cup Final and are already looking forward to welcoming Olympic soccer to Wales next year.
“The Millennium Stadium now plays a crucial role in helping to confirm Wales as a nation capable of hosting major events successfully.
“In a few weeks’ time the stadium will host two concerts by Take That which is yet more proof of the incredible versatility of the venue.
“The stadium is wholly owned and operated by the WRU and we can take credit as an organisation for utilising that asset properly and effectively in a highly competitive commercial environment.
“Images of the stadium are now seen around the world on television screens featuring the events we host and our nation benefits both financially and culturally by its impact.
“The Rugby World Cup is one of the biggest sporting events around and I want to congratulate the RFU for their success is securing such a prestigious event.”
