The sailor will start the 70-day relay at Land's End on May 19 and will be the first of 8,000 torchbearers as it visits towns and cities throughout the country.
"I am extremely honoured to be the first torchbearer at the start of the 70-day Olympic torch relay," said the 35-year-old. "It will be an amazing experience to be able to carry the Olympic flame in the area that I grew up in. I also want to congratulate the thousands of other inspirational people who will carry the torch this summer and bring the excitement of the Games to streets."
Lord Seb Coe, the London 2012 chairman, was pleased to announce Ainslie as the first torchbearer, while it was also revealed Scots cyclist Sir Chris Hoy will run with the torch through Manchester.
"Ben is the perfect person to start the relay in Land's End as he grew up in the area and is an inspirational sportsman who has worked hard," said Lord Coe. "He will kick-off what will be an amazing celebration."
The planned route has long been in place and the torch will come within 10 miles of 95% of the population before entering the Olympic Stadium during the opening ceremony on July 27.
The torch was lit yesterday at a ceremony at Olympia in Greece and is due to arrive in Britain on May 18. An actress, dressed in floor-length pleated robes, lifted the burning torch from a parabolic mirror as if the light had been beamed by the Gods directly from the sun's rays. Only a select group of dignitaries witnessed at first-hand the flame almost automatically burst in to life in front of the Temple of Hera. They included a 15-strong delegation from London, led by Lord Coe.
Only birdsong could be heard as the ritual ceremony was played out in scorching sunlight and the ancient ruins. A solo flautist played as the delegation returned to their seats in the ancient stadium to see the priestesses execute a graceful ritual dance. The flame was placed in an urn, before the high priestess and priestesses gently carried it to the stadium where it was hit by a gust of wind. Then there was a puff of smoke. It was relit from the mother flame.
The first torchbearer was Spyros Gianniotis, Greece's England-born world champion swimmer. The 32-year-old, who has already booked his place at London 2012 which will be his fourth-consecutive Olympics, proudly set off via Pierre de Coubertin's Grove. He passed it on to 19-year-old Alex Loukos, who was one of the 30 children who travelled to Singapore in 2005 as part of the closing presentations for London's bid. "For us this is now the best part of a decade," added Lord Coe. "This is an extraordinary journey."
International Olympic Committee president Jacques Rogge described the lighting as "the final countdown to a dream" which started seven years ago.
That dream will very soon become a reality.