The announcement comes as Wales’ four professional sides aim to survive the threat of cutting the number of teams to three or even two.
Ospreys have this week received planning permission from Swansea council to redevelop St Helen’s.
Cardiff are currently owned by the Welsh Rugby Union (WRU) after going into administration in April, while Dragons have been the least successful side since the inception of regional rugby in 2003.
Scarlets say they will continue to work constructively with the WRU on the structural review but are “driven by the ambition to grow the club and safeguard its future.”
“Scarlets is a rugby club that has been at the forefront of Welsh rugby and an integral part of the community of west Wales for more than 150 years,” said Scarlets chief executive Simon Muderack.
“We are fiercely proud of what this club stands for and will continue to protect that legacy.
“This partnership is the start of a new era for our club, strengthening our position with new investment, new ideas and a shared ambition to return the Scarlets to the top of European rugby.
“The new deal with HOL puts the Scarlets in control of its own future as we act boldly to move forward with a partner that will add significant resources and ambition.
“Crucially, it enables a future where Scarlets will continue to play in Llanelli, retain Scarlets’ strong identity and represent the whole of west Wales with pride.”
A WRU statement said: “We are pleased to welcome House of Luxury LLC into the Welsh rugby family after the positive news today they will be forming a new investment partnership with the Scarlets.
“We continue to work constructively with the Scarlets and all of our professional clubs on the structural review of our professional game we are currently undertaking and remain focused on the formal consultation process which begins shortly.”
