"It's on!" Ortiz said on Twitter.
While on ESPN's "MMA Live" in February, Ortiz said his next fight would be his last. Ortiz also revealed who he would most like to face in his final bout.
"Forrest Griffin! There's another trilogy," Ortiz said. "I won the first one. He barely skimmed away with the second."
Ortiz defeated Griffin by split decision in April 2006 at UFC 59. The bout received Fight of the Year honors.
Griffin returned the favor during their rematch, earning a split decision, on Nov. 21, 2009, at UFC 106.
The 37-year-old Ortiz made his mixed martial arts debut at UFC 13 on May 30, 1997. He defeated Wes Albritton by first-round TKO.
Ortiz, who has lost two fights in a row, is 16-10-1.
Griffin, also a former UFC light heavyweight titleholder, will look to rebound from a first-round knockout loss to Mauricio Rua on Aug. 27.
Since defeating Quinton Jackson in July 2008 to claim the title, Griffin (18-7) has struggled -- dropping three of five fights.