Leeds Tykes have secured a £400,000 extension to their sponsorship deal with the Leeds & Holbeck Building Society.
The building society have been the Tykes' main backers since the club's promotion to the Zurich Premiership in 2001 and the new agreement will prolong that support for two years.
The arrangement underlines the progress made by the Tykes since their elevation to the top flight and comes as the club prepare for their first Heineken Cup campaign.
Tykes chief executive Gary Hetherington said: "It's a tremendous day for the club.
"We are delighted that Leeds & Holbeck Building Society have agreed to continue their support of the club.
"They have been with us since our entry to the Premiership and have shown a lot of faith in the Tykes.
"That faith has now been rewarded. This is one of the biggest sponsorships in Premiership rugby and we hope this partnership can help take us forward."
Hetherington is confident that after establishing themselves as a Premiership club, the Tykes can go on this season and make their mark in Europe.
"The developments over the summer both on the field and now off the field are very significant," he added.
"They have given us a good platform to be successful this year."
Commenting on the new sponsorship deal, Leeds & Holbeck chief executive Ian Ward said: We are absolutely delighted. We've had a lot of coverage and it's been a great sponsorship over the two seasons."
"We are proud of the achievements made by the Tykes over the past few years and our continued sponsorship reflects our commitment to the club and its supporters."