One lucky person from each of the home nations who signs the shirt online will also win a VIP trip for two to the third and final Test against the Springboks.
With the Lions squad leaving in less than two weeks, there could not be a better time to back the Lions.
Three-time Lions tourist O'Driscoll, who knows all about the lure of the iconic red jersey, said: "The Lions tour to South Africa this summer is sure to be another titanic battle, and nothing can beat the feeling of touring with the Lions, not least to the backyard of the World champions.
"I can vividly remember the drama and excitement of the last Lions tour to South Africa 12 years ago, as well as captaining the Lions on the last tour, and with the launch of today's initiative to get behind the shirt, HSBC has provided a perfect opportunity for fans to get involved this summer.
"That's why I am calling on all fans, whether they are supporters of England, Scotland, Ireland or Wales, to show their support for the squad and sign the shirt."
The giant shirt, which is sure to become an iconic sight over the next two months, will spend the next four weeks touring around Ireland and the British Isles, before heading to South Africa to follow Ian McGeechan's squad as they travel throughout the country.
It will be making appearances in cities throughout England, Ireland, Scotland and Wales.
With the Lions coaching team, and the squad all signing the shirt in due course, now is the time for fans and supporters to have their name up alongside the greatest rugby players and to truly follow this summer's British & Irish Lions tour.
Your name will then be printed onto the giant replica before it heads off to South Africa in June.
Signees will also be entered into a prize draw to win four sought-after trips to go to South Africa for the third and final Test in Johannesburg - with one winner from each home nation.
This eagerly-anticipated 2009 Lions tour kicks off on May 30 with ten games around South Africa.
Three Test matches will take place against South Africa on Saturday June 20, Saturday, June 27 and Saturday, July 4.
As well as the giant shirt, HSBC has launched the world's biggest schools rugby programme, the HSBC Rugby Festivals.
Staged across the UK and Ireland, over 60,000 children will have participated by the start of the tour.
HSBC is Principal Partner and shirt sponsor of the British & Irish Lions tour to South Africa.