He entered the PRIDE 2005 Middleweight Grand Prix tournament as an underdog. For the first round of the tournament at "PRIDE Total Elimination 2005", he faced Quinton Jackson, whom he had challenged after Jackson won a controversial split decision over Murilo Rua at "PRIDE 29". Maurício dominated the favored fighter from beginning to end, breaking Jackson's ribs with knee strikes and ending the fight in dramatic fashion with soccer kicks to the face in the first round. Jackson later said that Shogun was the best fighter he had ever fought. In the second round at "PRIDE Critical Countdown 2005", Rua faced Antônio Rogério Nogueira, a member of Chute Boxe's rival academy Brazilian Top Team. Rua defeated Nogueira by unanimous decision. On 28 August 2005, Rua participated in "PRIDE Final Conflict 2005", in which the last two bouts of the tournament were held on the same night. Rua defeated Alistair Overeem by TKO in the first round, while Ricardo Arona defeated Rua's teammate Wanderlei Silva by decision. Rua and Arona faced each other in the final bout of the tournament. At 2:54 in the first round, Rua knocked Arona out with punches to win the bout and become the 2005 Middleweight Grand Prix Champion. He received a black belt in Brazilian jiu-jitsu from Nino Schembri afterwards, a process that only took him four years from when he got his purple belt. This wrapped up a year in which he won Fighter of the Year honors from Sherdog.com.