The All-American lineman, who spoke to ESPN and the New York Times, is eligible for the NFL draft in May and, assuming he is selected, would become the first openly gay player in the league's history.
"I understand how big this is," he tells ESPN. "It's a big deal. No one has done this before. And it's kind of a nervous process, but I know what I want to be. ... I want to be a football player in the NFL."
Sam, 24, had already told close friends and last August came out to his teammates during a preseason training camp when the coaches asked players to tell "a little about ourselves."
"And their reaction was like, 'Michael Sam finally told us,'" he recalls to ESPN. "They supported me from day one. I couldn't have better teammates. ... I'm telling you what: I wouldn't have the strength to do this today if I didn't know how much support they'd given me this past semester."
The Texas-raised, 6' 2", 260-lb. senior leaves Missouri as one the nation's top college players. He was defensive player of the year in the Southeastern Conference and his teammates voted him most valuable player. He is predicted to be drafted into the NFL in the third round this May.
"I just want to make sure I could tell my story the way I want to tell it," he tells the Times. "I just want to own my truth."
On Monday, First Lady Michelle Obama Tweeted her support.
"You're an inspiration to all of us, @MikeSamFootball. We couldn't be prouder of your courage both on and off the field. -mo," she wrote.
Ellen DeGeneres followed suit, writing, "Happy to hear the news about Michael Sam, who might become the first openly gay NFL player. #Respect. @MikeSamFootball."
Joe Robbins / Getty
Last spring, NBA player Jason Collins became the first athlete in a major pro sport to come out, though at the time he was a free agent and has not played since.