The five-time Olympic gold medallist, considered one of the world's greatest swimmers, revealed he had been secretly preparing for the brutal bluewater classic.
"I've spent my life in and around water, but this is a completely different test, both mentally and physically," said the 43-year-old, who will be making his race debut.
"Joining the LawConnect team is an opportunity to push myself, learn something new, and be part of an incredible Australian sporting tradition."
More than 130 yachts are due to depart Sydney on December 26 for the event's 80th edition, heading down Australia's east coast before tackling the notorious Bass Strait towards the Tasmanian state capital Hobart.
It can often be a wild 628-nautical-mile race, with two sailors last year dying in separate incidents as boats were pummelled by gale-force winds and big waves.
Thorpe will be on board one of five ultra-fast 100-foot supermaxis competing for line honours, with LawConnect targeting a third straight victory.
"Thorpie is one of Australia's greatest athletes," said LawConnect owner and skipper Christian Beck, who has a history of welcoming newer sailors on board.
"Having him join LawConnect not only brings an incredible story to this year's race but highlights our commitment to doing things differently."
