The agreement means that HSBC are the first principal partner to ever renew a sponsorship with the Lions and will see the bank become shirt sponsors of the team once again.
The partnership was formally announced at a joint media conference with the British Lions Limited (BLL) committee at HSBC Private Bank in London.
BLL also confirmed that the Lions will make history by opening the 2013 tour by playing their first ever match in Hong Kong, with the world-renowned Barbarians providing the opposition.
Meanwhile, former Scotland and Lions full-back Andy Irvine, who made an amazing 41 appearances (36 provincial and 5 Test matches) for the Lions, will be tour manager to Australia in 2013, taking over from Gerald Davies, who performed the role during the tour to South Africa last year.
Davies, the flying Welsh winger and a Lion in 1968 and 1971, was in turn appointed Chairman of BLL.
Sandy Flockhart, Executive Director for HSBC Holdings plc, said: "We are delighted to renew our association with one of the world's greatest ever sporting events.
"Today's announcement is a demonstration of the continued international appeal of the British & Irish Lions, and HSBC is committed to building on the successful relationship that was forged on last summer's tour to South Africa.
"I have no doubt that the next three years will be an exciting journey for both HSBC and the Lions, and in particular we are looking forward to welcoming the Lions and the Barbarians to Hong Kong for an historic fixture."
John Feehan, Chief Executive of BLL and the Six Nations, said: "It is a mark of the partnership that we have built with HSBC that we are able to announce this sponsorship renewal almost three years ahead of the next tour to Australia.
"We look forward to working with HSBC over the coming months to ensure that the Lions tour to Australia in 2013 is a success off the pitch, as well as on it.
"To be able to confirm today that the Lions will also break new ground with the first ever fixture in Hong Kong will ensure that the tour to Australia is even more special and includes even more fans.
"I would also like to congratulate Andy Irvine and Gerald Davies on their appointments today, and believe that the Lions will benefit hugely from having two highly-regarded and respected former Lions at the helm for the build-up and during the tour to Australia."
"Last year's tour was a phenomenal showcase for rugby, and I look forward to upholding the best of Lions traditions when we travel to the home of the Wallabies for what will be a fantastic experience.
"In the meantime, I can't wait to get my teeth into the planning and logistics that will be so crucial to the success of the tour over the next two-and-a-half years."
John Spencer, Chairman of the Barbarians, is certainly excited about the tour curtain-raising game in Hong Kong:
"The Barbarians and the Lions have a rich history and both share a unique place in the game of rugby," he said.
"To bring two such sides together and be able to create history in Hong Kong is very special indeed, and it will be an incredible occasion and the perfect way to kick off the 2013 Lions tour.
"We are proud and delighted to be part of such an innovative chapter in Lions history and are already looking forward to the match."
Trevor Gregory, Chairman of the Hong Kong Rugby Union, added: "It is a great honour to welcome the legendary Lions and the Barbarians to Hong Kong in 2013.
"The match will be another milestone for Hong Kong rugby and I am confident that our fans, and those from around the world, will enjoy this unique opportunity to witness the world's top players lining up for sides that have played such a definitive role in rugby history.
"When you throw in Hong Kong's reputation as one of the most famous - and festive - of global rugby destinations, rugby magic is in the making."
Four Lions players of past and present - Simon Shaw, Gavin Hastings, Jamie Roberts and Tommy Bowe - attended today's announcement, representing the unique spirit of the Lions in combining four home countries in one.
Ireland winger Bowe, who played in all three Lions Tests last year, said: "The Lions tour to Australia is a mouth-watering prospect; I will be going all out to ensure my involvement in another chapter of Lions history.
"For HSBC to be supporting this tour once again and for a match to be played in Hong Kong are both hugely exciting developments.
"I can't wait for 2013 to come round and in the meantime I will be doing my best to earn my spot on the plane to Australia."