The 37-year-old country singer from Belton, Missouri triumphed over runner-up Carly Rose Sonenclar in Thursday night's (December 20) live grand final.
Stevens said of his win: "First and foremost, I got to thank the man upstairs for taking care of me, my family, all the country music fans, God bless you and thank you so very much for all the votes. This is the best day of my life."
His mentor LA Reid said: "Congratulations to you, you deserve this... I think you represent The X Factor really well. So on behalf of myself, Simon [Cowell] and all of the judges, congratulations."
Sonenclar was tipped to win the show by Digital Spy readers earlier tonight, collecting over half of the votes in the final reader opinion poll of the season.
Host Mario Lopez also recognised 13-year-old Sonenclar's achievements, calling her a "little star" and reassuring her that she would have a bright future ahead of her.
Cowell's all-girl group Fifth Harmony, who were put together at the Judges' Houses stage of the competition, finished in third place.
The grand final also saw performances from special musical guests Pitbull and former X Factor UK finalists One Direction.
The X Factor USA will return to Fox for a third season in 2013. Open auditions will take place across the United States in March, April and May.