Armstrong was issued a life ban and stripped of his titles in August by the US Anti-Doping Agency (USADA), which last week revealed 1,000 pages of evidence against him, including testimony from 11 former teammates.
"Trek is disappointed by the findings and conclusions in the USADA report regarding Lance Armstrong," a statement from the bicycle manufacturer said. "Given the determinations of the report, Trek today is terminating our longterm relationship with Lance Armstrong. Trek will continue to support the Livestrong Foundation and its efforts to combat cancer."
Brewers Anheuser-Busch InBev, who used Armstrong in beer advertisements, said they would not renew a sponsorship deal with Armstrong when their current three-year endorsement contract ends in December.
"We have decided not to renew our relationship with Lance Armstrong when our current contract expires at the end of 2012," said Paul Chibe, Anheuser-Busch vice president of US marketing.
Both Nike and Anheuser-Busch said they would continue to support Livestrong, the charity Armstrong founded 15 years ago that has raised nearly $500 million.
Armstrong stepped aside rather than see Livestrong impacted by the fallout from revelations that a doping scheme was at the heart of his Tour de France triumphs from 1999-2005, the worst scandal in a sport tarred by cheating.
"To spare the foundation any negative effects as a result of controversy surrounding my cycling career, I will conclude my chairmanship," Armstrong said in a statement posted on the Livestrong website.
Armstrong is set to attend a gala fundraiser on Friday in Austin, Texas, to celebrate Livestrong's 15th anniversary in what could prove to be an emotional moment in the public spotlight, his first since scandal details were revealed.
"It has been a great privilege to help grow it from a dream into an organization that today has served 2.5 million people and helped spur a cultural shift in how the world views cancer survivors," Armstrong said.
More than 80 million of Livestrong's iconic yellow wristbands, launched in 2004 in collaboration with Nike, have been sold, donations that were in part inspired by Armstrong's now-tainted cancer comeback.