The Texan has won the Tour a record six times, and this year's race is always likely to be remembered for having been his last. Armstrong has admitted that in his 10th and last crack at the race, his objective is to "go out at the top of my game".
He will, he added during his pre-race press conference on Thursday, be taking part "to win, but also to have enjoyed my final Tour. I'm not chasing a legacy". That, after all, is already in the bag.
Part of his motivation, he said, is "a way of paying tribute to our team's new sponsor, Discovery Channel, who came into this business when I was on the point of quitting and knowing I was only around for one more Tour. Then I also want to win for my children, who will be on the race throughout for the first time this year, even if they don't really know what colour each jersey [for each of the separate competitions within the Tour] represents."
Should Armstrong be beaten in his final pursuit of the yellow jersey, the winner will be irrevocably linked to the 33-year-old as the man who foiled the American in his attempt to round off his career in perfect fashion.
But regardless of the outcome, six years of winning Tours is ample time for the Texan's achievements to have had a huge knock-on effect in areas hitherto untouched by cycling.
Armstrong got off to a remarkable start by making a comeback after suffering from testicular cancer - particularly because his explosion on to the Tour scene followed on the heels of the scandal-ridden 1998 race.
He formed the Lance Armstrong Foundation in 1997 to work with cancer sufferers, its most impressive success being the sale of yellow wristbands printed with Armstrong's motto - Livestrong. Priced at a dollar a throw, 50 million have been sold and they began an international fad for bracelets in all colours for a host of different causes. His popularity has soared to such an extent in the United States he is now rated 15th on Forbes magazine's list of the 100 most powerful celebrities.
But there is a darker side to the Armstrong story: the number of pending legal battles he faces when he retires, many of them connected with allegations of doping, runs into two figures, although with nothing but circumstantial evidence, they have boiled down to a question of opinion.
And although his fan ratings may be high in the States, he remains an unloved figure in France - at the end of last year's Tour, a poll placed him as the third most unpopular sports figure in the country.
"After he's gone, the Tour will recover interest it maybe has lost with Armstrong," Laurent Jalabert, the most prominent French cyclist of recent years, said.
"I'm not going to walk on water, I'm not a politician," was all Armstrong would say when asked if he wanted to be admired by 100 per cent of all cycling fans in France during this year's Tour. "I have had more support [in France] recently, and it's appreciated."
But the cynics might ask if the increase in cheering is because the public know that when he rides by it will be the last time they see him.
And what of the sport itself? Armstrong has concentrated so exclusively on the Tour, even bypassing last year's Olympic Games, that other events, such as the World Championships, have become almost completely eclipsed. How long will they take to recover their original status cannot be resolved until he takes his leave.
"Will I miss him?" Jan Ullrich, the rider who has come closest to beating Armstrong over the years, was asked on Thursday. "Of course - like many fans of the sport will, too.
"He's been the big star of the Tour for many years, and I hope that if he wins and has a party afterwards, I'll be invited."
For Armstrong, the 2005 Tour is already his farewell celebration. Quite how interesting it will be for the rest of us depends largely on how many of his rivals get to gatecrash it.
If all of them have had their fair share of injuries and illnesses in the past, not even Armstrong's meticulous build-up could prevent him from taking a tumble early last week.
Stung by a wasp while out training, he fell so hard on his head he broke his helmet, but he brushed aside his injuries, saying: "I'm ready, in form and maybe feeling stronger than usual."
Alasdair Fotheringham writes for 'Cycling Weekly'
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