'Triumphant (Get 'Em)' will be released at the beginning of August and features Rick Ross and Meek Mill.
"I wrote TRIUMPHANT when I was going through a difficult time & it helped me get through it. When u hear it, pay attention 2 the lyrics #WIN (sic)," she tweeted.
It's the first new material from Carey since 2009's Memoirs of an Imperfect Angel.
Meanwhile, the 'Touch My Body' star is close to finalising a deal to become a judge on American Idol, Deadline reports.
Carey, whose husband recently joked that she would be too expensive for Idol producers, is said to have negotiated a deal worth $17 million.
She has been linked with the show for some time after previously being considered for The X Factor USA.
Watch Mariah Carey's video for 'Obsessed' below: