He has also returned the silver medal he won with the US 4x100 metres relay team at the 2012 London Olympics.
As part of the suspension, Gay, the joint second fastest man in history, was disqualified from all competitive results since July 15, the date he first used a product that contained a prohibited substance.
The American 100 meters record holder had tearfully admitted last July he had failed an out-of-competition doping test, saying "I basically put my trust in someone and I was let down."
The 31-year-old could have been suspended for two years for his first doping offence but received a reduction because of his substantial assistance into the investigation of his case, USADA said.
"We are thankful he decided to come in and be truthful in his cooperation with us," USADA chief executive Travis Tygart told Reuters.
Gay will be eligible to return to competition in June of this year and will be eligible for future world championships and Olympics, Tygart said.
An investigation into the circumstances of his case is ongoing and his suspension is subject to appeal by the International Association of Athletics Federation and the World Anti-Doping Agency.
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