The cancer survivor made the announcement at the same time he announced the creation of the Livestrong Global Cancer Awareness Campaign, a campaign which focuses on supporting the 25 million people living with cancer worldwide, dispelling the misconceptions surrounding the disease and urging world leaders to make cancer a greater priority.
"I'm returning to cycling in order to raise awareness of the global cancer burden," Armstrong said at a New York news conference. "While my intention is to train and compete as fiercely as I always have, this time I will gauge victory by how much progress we make against cancer."
On the tour, Armstrong, 37, won the last of his seven Tour de France titles in July 2005.
He will rejoin Johan Bruyneel, his long time team director and the architect of his seven Tour de France wins, on Team Astana.
Armstrong has helped raise more than $260 million for the fight against cancer and distributed more than 60 million LIVESTRONG? wristbands to help make cancer a global priority.
Because of unpoven past doping allegations, he said that all his blood work and testing will be posted online at www.livestrong.com.
Notable deaths of 2014 [PHOTOS]