Murilo "Ninja" Rua (born May 22, 1980 in Curitiba, Brazil) is a mixed martial artist. He currently fights in EliteXC. He is the older brother of Mauricio Rua "Shogun". He is known for his well-rounded fighting skills, in particular Muay Thai and Brazilian Jiu-Jitsu.

Rua is a veteran of PRIDE Fighting Championships, where he once enjoyed a reputation as one of the strongest middleweights in the world. "Ninja" fights at 185 pounds, but has also fought at 205 pounds and heavyweight. He is the former Elite XC middleweight champion.

Murilo Rua started his career at Chute Boxe Academy in Curitiba, Brazil, a Muay Thai training group which has produced champions like Wanderlei Silva. Ninja's first foray into MMA was with Brazilian based Meca World Vale Tudo, there he amassed an impressive 5-0-1 record before signing with Pride Fighting Championships.

Ninja made his PRIDE debut against Daijiro Matsui in September 2001, which he won via referee stoppage after repeated kicks and stomps. After losing a close decision to Dan Henderson, Rua went on to defeat such fighters as Alex Andrade, Akira Shoji, Alexander Otsuka and Mario Sperry. The latter being the beginnings of the long lasting rivalry between Chute Boxe and Brazilian Top Team. Rua lost to Ricardo Arona in a close battle of attrition, and Sergei Kharitonov in the PRIDE Total Elimination 2004, where Ninja fought as a heavyweight.

At PRIDE 29 Fists of Fire he faced Quinton Jackson "Rampage". Jackson won via a split decision that did not seem to reflect the events of the match. Jackson appeared embarrassed with the result and attempted to offer the winner's trophy to Rua following the decision. Commentators such as Mauro Ranallo and Bas Rutten, who were present at the bout, also have stated that they thought Ninja won the encounter.

Rua fought three more times in PRIDE, defeating newcomer Murad Chunkaiev before dropping a lacklustre decision against top ranked Paulo Filho, nevertheless Ninja was selected as part of the PRIDE welterweight (185 pound) Grand Prix. In the opening bracket however he was knocked out by Denis Kang. Murilo Rua then left PRIDE for a tenure with British MMA promotion Cage Rage in order to strengthen the tie between the two promotions. His first bout, against English UFC veteran Mark Weir, resulted in a victory by submission after a rough and tumble affair.

He also defeated Alex Reid via doctor stoppage before the newly created EliteXC organisation purchased Cage Rage, therefore he fought for the vacant Elite XC middleweight at the StrikeForce-EliteXC - Shamrock vs. Baroni event against Greg Jackson trained Joey Villasenor and recorded a second round TKO, stopping him with strikes. After three months as the champion his first title defense came to ICON sport middleweight champion Robbie Lawler, despite narrowly winning the first two rounds, an exhausted Ninja was defeated via a third round TKO at EliteXC: Uprising. He rebounded with a victory over Muay Thai fighter and Cage Rage contender Xavier Foupa-Pokam at Cage Rage 24: Feel the pain.

On December 18 ,2007 , Sherdog.com reported that both Murilo and his brother Mauricio Rua have left the Chute Boxe camp with plans to open up their own facility in Massachusetts. The Ruas' new camp was named Universidade da Luta which translates to "University of Fighting" and instead was opened in the Ruas' hometown of Curitiba, Brazil.

Ninja was initially scheduled to fight Phil Baroni on the May 31st EliteXC card, however, he suffered a minor foot injury which led him to fight on the June 14th card instead. Where he recorded a dominant KO victory over undefeated Tony Bonello. On October 4, 2008, Murilo was defeated by Benji Radach on a live CBS broadcast. Radach finished the fight with punches to Murilo's head after a failed flying knee sent Ninja sprawling on his back.