The charges were brought by the US Anti-Doping Agency (USADA) which is now calling on the sport's governing body, the International Cycling Union (UCI), to take away the Texan's prestigious titles.
The Texan says he is the victim of a witch-hunt but his decision not to fight the allegations means his record will be forever tarnished as that of a cheat.
He said: "There comes a point in every man's life when he has to say, 'enough is enough'. For me, that time is now.
"I have been dealing with claims that I cheated and had an unfair advantage in winning my seven Tours since 1999."
Armstrong was known as a ferocious rider who never quit.
He won global admiration for his battle against cancer, returning to health to win cycling's most famous race seven times.
With his sporting record in tatters, his standing outwith cycling will also be tarnished.
Armstrong's Livestrong foundation, which helps cancer survivors, helped start the trend of charity wristbands and raised millions of pounds.
On Twitter, Sarra, the wife of Olympic cycling champion Sir Chris Hoy took a dig at Armstrong telling her 2000 followers: "I've won the TdF as many times as Lance Armstrong."
Lord Sugar reacted to the news the cyclist was giving in by saying: "Lance Armstrong says he can't be bothered to fight over drug allegations. Yeh right ... you would fight like crazy to retain your integrity."
Rugby's Mike Tindall said: "The biggest loser in the Lance Armstrong affair is the sport of cycling. To try and change results over the 15 years seems ridiculous."
Others defended Armstrong, saying he never failed a drugs test.
USADA based its case on eyewitness accounts that Armstrong, along with other leading Tour de France cyclists, were injecting themselves with the blood booster EPO, testosterone and other performance-enhancing drugs.
The UCI had backed the retired rider's legal challenge to the agency's authority to act.
But USADA chief executive Travis Tygart said the UCI now had "no choice but to strip the titles under the code". He said: "It is a sad day for all of us who love sport and athletes. It's a heartbreaking example of win-at-all-costs overtaking the fair and safe option. There's no success in cheating to win."
USADA has said previously that 10 of Armstrong's former team-mates were ready to give evidence against him, alleging he used banned substances as far back as 1996.
Armstrong came to transcend his sport after writing It's Not About The Bike, the inspirational story of his fight to survive testicular cancer in 1996 and go on to win his first Tour de France three years later.
His love life also saw him featuring in the gossip columns after he divorced his wife and mother of three of his children Kristin Richard.
He then became engaged to singer Sheryl Crow, only to split with her and father two more children with girlfriend Anna Hansen. He has also dated actress Kate Hudson.
Armstrong was named BBC Overseas Sports Personality of the Year in 2003. The BBC will not remove that title from him following his announcement.
Damien Ressiot, a sports reporter who first published doping allegations against Armstrong in L'Equipe, said: "Armstrong personified impunity. He was seen as too well protected to fall. So the big message today is that impunity is over."
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