Murilo Milani Rua (Portuguese pronunciation: [ˈʁuɐ]; born May 22, 1980), also known as Ninja, is a Brazilian retired mixed martial artist.

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, where 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.

[3] After returning from injury, he defeated Mario Sperry, and this fueled beginning 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 he fought as a heavyweight, suffering a brutal knockout loss.

Commentators such as Mauro Ranallo and Bas Rutten, who were present at the bout, also have stated that they thought Rua had won the fight.

Rua fought three more times in Pride, defeating newcomer Murad Chunkaiev before dropping a lacklustre decision against top ranked Paulo Filho.

He also defeated Alex Reid via doctor stoppage before the newly created EliteXC organization purchased Cage Rage, therefore he fought for the vacant Elite XC middleweight at Strikeforce: Shamrock vs. Baroni against Greg Jackson trained Joey Villasenor and recorded a second-round TKO, stopping Villasenor with strikes.

On December 18, 2007, Sherdog.com reported that both Rua and his brother Mauricio had left the Chute Boxe camp with plans to open up their own facility in Massachusetts.