The London 2012 200m gold medallist and world record holder will run a marathon a day from John O'Groats to Land's End for charity, starting in August.
The 36-year-old hopes to inspire others during the run, which will come a month after the Anniversary Games at the Olympic Stadium in July.
"I am quite dynamic as an athlete when competing and training," said Whitehead. "On the track at the moment we have got the Anniversary Games in July as well as the World Championships but I have my own personal challenge in August which is to run Britain.
"It seems a little bit crazy but I will be running 40 marathons in approximately 40 days and that is really to spread the message and the legacy of what I have done in my life as an athlete.
"It is about inspiring people to think more widely about themselves in sport and embrace new ideas.
"It is probably the biggest challenge (of my career). A thousand miles is a massive challenge for anybody to cycle never mind to run.
"I think transferring my skills from being a Paralympic gold medallist and world record holder through to running a thousand miles is going to be really tough but with the team around me hopefully we can pull in the same direction to be successful."
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