Premiership Rugby has moved into a "new era" after a deal was concluded for private equity firm CVC Capital Partners to invest more than £200m.
CVC have bought a minority shareholding, understood to be about 27%, after member clubs had previously rejected an offer to buy 51%.
"This is a landmark new partnership," Premiership Rugby chairman Ian Ritchie said of the deal.
"It is positive news for the league, the clubs and the game."
He continued: "It takes the clubs to a new level and is the heralding of a new era."
CVC has previously led investments in Formula 1 and elite motorcycling series Moto GP.
"They know global sports, and that is one of the things that attracted us to them," said Premiership Rugby chief executive Mark McCafferty.
"They have a track record in helping sports develop."
Premiership Rugby says the extra money will not result in a hike in player wages, but will instead go towards improving facilities at club level and growing the league globally.
"They key thing for the next few years is to build the facilities, the infrastructure and the investment in central marketing," added McCafferty.
Ritchie, who was previously CEO at the Rugby Football Union, says the deal will not damage relations between the clubs and the RFU.
"There has to be a partnership between clubs and the RFU, and that is the best way it works for English rugby," Ritchie added.
"I see this as complementary and not in any way competitive."