The Millennium Stadium is to be renamed the Principality Stadium from January 2016 after a 10-year sponsorship deal was announced.
Owned by a subsidiary of the Welsh Rugby Union, and home to the Wales team, the stadium in Cardiff was built for the 1999 Rugby World Cup and has also staged football matches and concerts.
The deal with the Principality Building Society sees it gain a title sponsor for the first time.
WRU chairman Gareth Davies said: "The stadium is an iconic landmark in Wales. The partnership with Principality will help the grass roots of the game."
The Millennium Stadium opened in June 1999 in time for the Rugby World Cup in Wales later that year.
The Millennium Commission's contribution to the building of a new national stadium was recognised in its original naming and Davies said: "It will be a challenge to embed the name into the Welsh psyche.
"But other grounds have managed it - look at the Aviva Stadium in Dublin - and we want to do that as soon as possible.
"The stadium enjoys a worldwide reputation and has become an international symbol for our nation, so it is highly appropriate that one of our principal partners now has even stronger links with Welsh rugby through these naming rights."
Davies declined to reveal the financial aspects of the deal but he said the game in Wales would benefit from the grass roots right through to the elite level.
Principality's commitment to Welsh rugby dates back to 1969 and has featured the sponsorship of the WRU's main knock-out cup competition since 2001 and the company's chief executive, Graeme Yorston, said it was unrealistic to see the word Millennium retained in the stadium's title.
"That was not an option for us because we are putting money into Welsh rugby," Yorston said. "Millennium had to get replaced by Principality.
"We share a strong history of shared values with the WRU and we are delighted to put our name to the home of Welsh rugby - a home that truly belongs to the nation and is at the heart of Welsh life."
The Millennium Stadium has been a well-used venue for major sporting and music events since the turn of the last century and will shortly host eight matches, including two quarter-finals, at the forthcoming Rugby World Cup.
The 2017 UEFA Champions League final will also be played at the stadium.