José Aldo was born on September 9, 1986, in Manaus, Brazil. As an infant, Aldo was dropped onto a barbecue, leaving a permanent scar on the left side of his face. Throughout his infant years, he was keen on football and wanted to become a professional. His aspirations were supported by his father. But Aldo grew tired of getting beaten up in fights on the street, thus starting to train capoeira to learn ways to defend himself better in brawls. Aldo used to train capoeira on the streets after the classes, once gaining attention of a Brazilian jiu-jitsu trainer. He invited Aldo to try one session of jiu-jitsu and after the session, Aldo decided to leave capoeira to start training jiu-jitsu. At the age of 17, Aldo moved from Manaus to Rio de Janeiro having only his clothes with him and determination to train mixed martial arts there until he achieved something in the sport. He is a teammate and training partner of former UFC Bantamweight champion Renan Barão at Nova União.

Known by the nickname “Junior”, José Aldo da Silva Oliveira Júnior fought his first professional MMA fight at the age of 17 at EcoFight 1 on August 10, 2004. He fought fellow countryman and newcomer Mário Bigola, whom he defeated by knockout in just 16 seconds into the first round. It would be Bigola’s first and only professional fight.

Aldo spent the next several years jumping from organization to organization. He next fought Vale Tudo and Shooto veteran Aritano Silva Barbosa, who had lost four of his last five fights, at Rio MMA Challenge 1 on May 12, 2005. Aldo landed two knees to the chin of Barbosa in the opening seconds of the fight, sending him to the canvas where Aldo swarmed with punches. Barbosa attempted a single leg takedown, but Aldo pulled away and threw two soccer kicks to the prone Barbosa before the referee stopped the fight at twenty seconds of the first round, awarding Aldo the victory via knockout. Less than two months later Aldo fought newcomer Anderson Silvério at Meca World Vale Tudo 12. He also defeated Silvério with soccer kicks, 8:33 into the first round.

Aldo then traveled to England, where he fought Micky Young at FX3- Battle of Britain on October 15, 2005. He defeated Young just 1:05 into the first round by TKO (punches).

Only a month later, in November 2005, Aldo went up a weight class to lightweight and fought respected Luta Livre black belt Luciano Azevedo at Jungle Fight 5. Aldo won the first round, winning most of the exchanges with solid combinations and leg kicks and stuffing Azevedo’s numerous takedown attempts (he was nearly taken down early in the round, but appeared to purposefully fall out of the ropes to force a restart from the referee), as well as landing a solid knee as Azevedo went for a takedown. Aldo shrugged off Azevedo’s first few takedown attempts in the second, but was eventually taken down against the ropes by a double leg. Aldo raised his hips up looking for triangles and other submissions, but Azevedo easily defended.

Aldo rebounded in his next fight, returning to featherweight against the then-undefeated Thiago “Minu” Meller at Gold Fighters Championship I on May 20, 2006, winning a unanimous decision in a very close fight. Round one could have gone either way, with Aldo getting two takedowns (both times getting into half-guard) and cutting Meller’s right eyebrow with a left hand. Meller went for two armbars, nearly hyper-extending Aldo’s right arm in the first attempt before Aldo was able to escape. Aldo won a lackluster round two, again taking Meller down and landing some hammerfists. A seemingly exhausted Aldo stalled against the ropes much of the third round, holding Meller in the clinch. Both landed some solid strikes in the few exchanges there were in the round.

Aldo made his debut for mixed martial arts promoter World Extreme Cagefighting on June 1, 2008 at the Arco Arena in Sacramento, California. In his debut with the organization he defeated renowned fighter Alexandre Franca Nogueira at WEC 34. Aldo won his fight on June 7, 2009 at WEC 41 against Cub Swanson via double flying knee eight seconds into the first round.

Aldo won the WEC Featherweight Championship against Mike Brown on November 18, 2009 at WEC 44. He won by TKO in the second round. He was able to get Brown in the back mount, where he landed a barrage of punches, ending the fight at 1:20 of the round. José Aldo was the recipient of Fighter of the Year accolades for 2009 from both MMA Live and Sherdog.com.

Aldo faced former title holder Urijah Faber on April 24, 2010 at WEC 48. Aldo defeated Faber via unanimous decision (49–45, 49–45, and 50–45). Aldo was able to use effective leg and body kicks (a total of thirty-two) to stifle Faber, sending him to the canvas several times with solid kicks. For the remaining 1:40 of the fourth round Aldo trapped Faber in the crucifix, peppering him with punches and elbows. Aldo did not engage most of the fifth (although he did land a body shot that nearly crumpled Faber). This was Aldo’s first decision win in his WEC career.

Aldo defended his title against Manvel Gamburyan by KO at 1:32 of the second round on September 30, 2010 at WEC 51.

On October 28, 2010, World Extreme Cagefighting merged with the Ultimate Fighting Championship. As part of the merger, all WEC fighters were transferred to the UFC. Aldo became the inaugural UFC Featherweight Champion, receiving the first ever UFC featherweight title belt on Saturday, November 20, 2010 at UFC 123. His first defense was set to take place at UFC 125 against Josh Grispi. Aldo was forced to withdraw from UFC 125 after suffering a neck injury.

Aldo made his first title defense against Mark Hominick on April 30, 2011, at UFC 129 by defeating the Canadian by a unanimous decision in a bout that earned Fight of the Night honors.

Aldo had his second title defense against Kenny Florian on October 8, 2011, at UFC 136, where he won by unanimous decision.

Aldo next faced Chad Mendes on January 14, 2012, at UFC 142, Aldo won via KO in the final second of the first round. His post-fight celebration, where he sprinted out of the cage and into the crowd at the HSBC Arena in Rio, is regarded as one of his most iconic moments as champion.

Aldo is married to Vivianne Perreira, who has a purple belt in jiu-jitsu and has fought twice professionally in Muay Thai. Their daughter Joanna was born in 2012. Aldo is an avid football fan. In Brazil, he is well known as a supporter of Clube de Regatas do Flamengo and English Premier League club Chelsea FC.

Aldo was expected to face Anthony Pettis on August 3, 2013, at UFC 163. However, in mid-June Pettis pulled out of the bout citing a knee injury and was replaced by Chan Sung Jung. Aldo defeated Jung via fourth-round TKO, finishing Jung with a flurry of strikes after Jung suffered a dislocated shoulder while throwing an overhand right.

On February 1, 2014, at UFC 169 Aldo defended his title by defeating Ricardo Lamas by unanimous decision (49–46, 49–46, and 49–46).

A rematch with Chad Mendes was expected to take place on August 2, 2014, in the event headliner at UFC 176. However, in early July, Aldo pulled out of the bout with an injury. The rematch with Mendes was subsequently rescheduled and took place for October 25, 2014 at UFC 179. Despite getting dropped in the first round and being rocked in the third, Aldo scored two knockdowns of his own, one in the first and the other in the third and also rocked Mendes throughout the fight, winning four of the five rounds in the eyes of the judges thus taking the fight by unanimous decision (49–46, 49–46, and 49–46). The win also earned him his third Fight of the Night bonus award, and was selected Fight of the Year by multiple MMA outlets.

To date, Aldo has defended 91% of his opponents’ takedown attempts. On September 28, 2014, at Nova União, under the tutelage of Mestre Roberto Leitão (10th Dan), Daniel F. A. Malvino “Pirata” (1st Dan), Marco Ruas (7th Dan) and Daniel D’dane (4th Dan), Aldo was awarded his black belt in Luta Livre. His Luta Livre instructor lineage is as follows: Roberto Leitão Sr. → João Ricardo N. de Almeida → Marco Ruas → José Aldo.

Aldo was scheduled to face Conor McGregor on July 11, 2015, at UFC 189. On June 30, Aldo pulled out of the fight, citing a rib injury which makes him unable to fight. Chad Mendes took his place and was defeated by McGregor for an interim title. Aldo faced McGregor in a title unification match on December 12, 2015, at UFC 194. He lost the fight via knockout 13 seconds into the first round, resulting in his first defeat in over ten years and his first ever loss at featherweight, ending a 15 fight win streak in the division.

Aldo faced Frankie Edgar in a rematch on July 9, 2016, at UFC 200 for the interim UFC Featherweight Championship. Aldo won the fight by unanimous decision (49–46, 49–46, and 48–47). On November 26, 2016, reigning UFC Featherweight Champion Conor McGregor was stripped of the title after winning the UFC Lightweight Championship, having never defended the Featherweight belt since he won it in December 2015. As a result, Aldo was promoted to Featherweight Champion.

Aldo faced interim featherweight champion Max Holloway in a title unification bout on June 3, 2017, in the main event at UFC 212. After winning the first two rounds on all three judges scorecards, he lost the fight by TKO in the third round. Despite the loss, the fight earned Aldo his fourth Fight of the Night bonus award. This was Aldo’s 3rd loss in his 29 fight career.

Aldo was scheduled to face Ricardo Lamas on December 16, 2017, at UFC on Fox: Lawler vs. dos Anjos. However, Aldo was pulled from the bout in favour of a rematch with Holloway two weeks earlier at UFC 218, replacing an injured Frankie Edgar. Similarly to the first fight, Aldo found success in the opening rounds before slowing down and losing the fight via TKO in the third round.

Aldo faced Jeremy Stephens at UFC on Fox 30 on July 28, 2018. The fight was Aldo’s first non-title (three round) fight in over nine years. Aldo won the fight by TKO after a left hook to the body dropped Stephens, and the fight was stopped due to subsequent strikes from Aldo. This win earned him the Performance of the Night award.

Aldo faced Renato Moicano on February 2, 2019 in the co-main event at UFC Fight Night 144. He won the fight via TKO in the second round. This win earned him the Performance of the Night award.

Aldo faced Alexander Volkanovski at UFC 237 on May 11, 2019, in Rio de Janeiro, Brazil. Aldo lost the fight via unanimous decision.

On June 24, 2019, it was announced that Aldo had signed a new exclusive eight-fight contract with the UFC prior to his bout with Volkanovski. This marked a major deviation from Aldo’s previous firm stance on retiring by the end of 2019, in which he stated “I had already planned to stop when I was 30 years old and begin something else. I’m at a point where I have to make a decision, and nothing is going to change my mind. Martial arts is always going to be a part of my life, but everything has a beginning, a middle and an end. And I see this coming to an end.”

On October 23, 2019, it was announced that Aldo would be moving down to the Bantamweight division. He faced Marlon Moraes at UFC 245 on December 14, 2019. He lost the largely contested bout via split decision.

Aldo was expected to face UFC Bantamweight Champion Henry Cejudo on May 9, 2020 at then UFC 250. However, Aldo pulled out on April 8 due to visa issues as the event was expected to be moved to the United States due to the COVID-19 pandemic. Following Cejudo’s title defense against Dominick Cruz at UFC 249, Cejudo announced he would be retiring from active mixed martial arts competition and he vacated the UFC bantamweight championship. The UFC then announced that Aldo would be facing Petr Yan at UFC 251 on July 12, 2020, for the vacant bantamweight title. Aldo lost the bout via technical knockout in round five.

Aldo is expected to face Marlon Vera on November 21, 2020 at UFC 255.