Armstrong finished 40 minutes behind winner Alberto Contador
Seven-time Tour de France winner Lance Armstrong has announced he is to retire from cycling for a second time.
The 38-year-old American quit the sport in 2005 before returning last year but he announced last month that 2010 would be the last time he rode the Tour.
Armstrong finished 40 minutes behind winner Alberto Contador in 23rd place.
"This race has been good to me but I can't lie - I'm ready to retire part two," said Armstrong, who crashed on a number of occasions during the race.
"I was just glad that three weeks of suffering is over and I get to go home. I don't have to stress about racing every day.
"I have a lot of happiness, a lot of good memories, just a lot of good times here."
I'm 100% confident. I know what I did and didn't do
The Texan saw his hopes of a record eighth win disappear on the eighth stage of his 13th Tour after he fell twice and lost nearly 12 minutes on the leaders.
On Tuesday, he was denied his first stage win since 2005 when Frenchman Pierrick Fedrigo edged him out in a thrilling sprint finish on stage 16.
In 1996 Armstrong had been given less than a 50-50 chance of survival after being diagnosed with testicular cancer as the disease spread to his lungs and brain.
However, after an aggressive bout of chemotherapy, he made a full recovery and returned to the sport in early 1998, going on to dominate the race from 1999 to 2005.
He set up the Livestrong cancer charity which gained international recognition as the organisation's distinctive yellow wristbands were worn by millions of people worldwide.
Last year he rode for the Astana team but after a public dispute with team-mate Contador he left to form his own team, backed by American retailer RadioShack.
"Whatever he does, he is a story. He is an incredible character," said Frenchman Alain Gallopin, one of RadioShack's sports directors.
However, when Armstrong returns home he will have to face more doping allegations that have dogged him throughout his career.
A US federal investigation is focusing on whether Armstrong, who has never tested positive, used government money to dope and win his seven Tours with the US Postal team.
The government probe follows allegations made by Armstrong's former team-mate and disgraced 2006 Tour winner Floyd Landis.
"I can assure you that there is not going to be a teary-eyed confession from me", said Armstrong, who has hired a criminal defence attorney to fight the allegations.
"I'm 100% confident. I know what I did and didn't do. And I know that the press is incredibly sensational. I'm not a fool, that's what they need, that's OK. In the end it will all come out.
"We will certainly field the best team but in the end it's a fair competition, that's why ultimately - maybe not yet, maybe not right now - but ultimately it will be a fair competition and I'll get my chance to speak about it."