Mauricio "Shogun" Rua originally came to the UFC in 2007 as the #1 light heavyweight in the world. He'd been Pride's rising star in the division since 2005 when he won their Middleweight (205lbs) Tournament by beating Quinton "Rampage" Jackson, Alistair Overeem and Ricardo Arona. No one expected The Ultimate Fighter winner Forrest Griffin to have much of a chance against Shogun, but Forrest shocked the world by finishing Rua at UFC 76 and then going on to win the UFC title. Since then their individual fortunes have risen and fallen with both winning and quickly losing the championship belt. Now they meet again according to MMA Fighting:

Early Friday morning, UFC president Dana White confirmed the bout to MMA Fighting.

Forrest Griffin (18-6) [Num. 6]
Win Rich Franklin - Decision (Unanimous) UFC 126
Win Tito Ortiz - Decision (Split) UFC 106
Loss Anderson Silva - KO (Punch) UFC 101

Mauricio "Shogun" Rua (19-5) [Num. 2]
Loss Jon Jones - TKO (Punches and Knees) UFC 128
Win Lyoto Machida - KO (Punches) UFC 113
Loss Lyoto Machida - Decision (Unanimous) UFC 104

Aug 27th, live on Pay-per-view from Rio de Janeiro, Brazil:

Anderson Silva vs. Yushin Okami
Mauricio Rua vs. Forrest Griffin
Takanori Gomi vs. Edson Barboza

UFC: Rio coverage