The move comes a week after the U.S. Anti-Doping Agency said it had uncovered overwhelming evidence of Armstrong's involvement in a sophisticated doping program while a professional cyclist.
Lance Armstrong said Wednesday that his decision to step down from the Livestrong cancer charity he founded was to "spare the foundation any negative effects as a result of controversy surrounding my cycling career," according to a statement posted to the group's website.
Nike has also ended its contract with Lance Armstrong.
"Due to the seemingly insurmountable evidence that Lance Armstrong participated in doping and misled Nike for more than a decade, it is with great sadness that we have terminated our contract with him," the company said in a statement Wednesday. "Nike does not condone the use of illegal performance enhancing drugs in any manner."
Armstrong found out he had testicular cancer at age 25 when he was emerging as a rising star among cyclists.
He started a small group to raise money for cancer called the Lance Armstrong Foundation in 1997.
Since then, 84 million bright yellow Livestrong wristbands have been distributed.
According to the Texas-based charity, Armstrong has helped raise millions of dollars for cancer research, treatment and support in his role as Livestrong founder and helped "dispel the stigma and misconceptions about the disease."