Diogo Reis was born on March 20, 2002, in Manaus, Amazonas, Brazil — a city not traditionally associated with the epicenters of competitive jiu-jitsu, yet one that would produce one of the sport's most decorated modern competitors. His introduction to the art came at age 10, sparked by his older brother's training, which gave the younger Reis his first glimpse of what the sport could offer. That early inspiration set in motion a trajectory that carried him from the gyms of Manaus to the highest stages of global grappling.

Reis began his formal training under coach Alexandre Oliveira, building the technical foundation that would later support a decorated career. He eventually transitioned to the academy of Melqui Galvão, whose Manaus-based team had become a breeding ground for elite talent. Under Galvão's guidance, Reis sharpened his skills against high-level training partners and prepared for the rigors of international competition. The unconventional geography of his upbringing — far from the established BJJ hubs of São Paulo or Rio de Janeiro — added a layer of determination to his development. Building a world-class career from Manaus demanded deliberate effort and a willingness to travel and compete against the best from an early age.

Before his name carried weight on the black belt circuit, Diogo Reis had already distinguished himself as one of the most accomplished young competitors of his generation. Competing through the juvenile and colored belt divisions, he systematically conquered the four tournaments widely recognized as jiu-jitsu's Grand Slam — the IBJJF World Championship, the IBJJF Pan Championship, the CBJJ Brazilian Nationals, and the IBJJF European Open — a sweep that very few competitors manage at any level, let alone as teenagers.

His juvenile World Championship titles came in back-to-back years, 2018 and 2019, establishing him as the dominant force in his age group globally. He paired those with a Pan Championship juvenile title in 2019, a European Open juvenile title the same year, and the CBJJ Brazilian Nationals juvenile crown, also in 2019. Earlier teen-division titles at the Brazilian Nationals in 2015 and 2016 demonstrated that his competitive edge had been present almost from the moment he began competing. At the international level, he also claimed the IBJJF Pan Kids Championship in 2017 and the IBJJF American Nationals Teen 3 title that same year.

As he progressed into the colored belt adult divisions, Reis continued his winning ways. At brown belt in 2020, he captured both the FAJJ Copa America GI and NOGI titles, rounding out a lower-belt résumé that left little doubt about his readiness for the black belt stage. The Grand Slam sweep as a teenager was not merely a statistical achievement — it was a signal to the broader community that a generational talent had arrived.

Diogo Reis's black belt promotion arrived on December 13, 2020, when Melqui Galvão tied the belt around his waist at age 18. The timing carried its own significance: Reis had made his black belt competitive debut one week earlier, on December 6, 2020, at the AJP Tour Grand Slam tournament in Rio de Janeiro, earning a silver medal — a strong entry point that signaled his readiness for the professional tier even before the official ceremony.

The transition from colored belt prodigy to black belt competitor was swift and largely seamless. In 2021, Reis wasted little time accumulating victories at the professional level, claiming gold at the AJP Abu Dhabi World Pro, the AJP Grand Slam in Miami, and the AJP Grand Slam in Rio de Janeiro. He also won the ADCC Balneário Brazil Trials in 2021, securing qualification for the premier submission grappling event in the world. These early victories confirmed that his juvenile dominance was not a ceiling but a foundation — and that his best performances were still ahead.

The environment in which Diogo Reis developed was defined as much by his training partners as by his coaches. At Melqui Galvão Jiu-Jitsu, he trained alongside talents including Mica Galvão and Fabricio Andrey, forming part of a Manaus-based squad that punched well above its regional weight on the international circuit. The collective quality of the team accelerated individual development, with each athlete pushing the others in daily training.

In 2022, the team entered a partnership with Fight Sports, an affiliation that brought broader international exposure, increased resources, and greater visibility during a period when several of its members were ascending to the sport's top ranks. By early 2023, however, Melqui Galvão chose to separate from that arrangement and establish an independent association under his own name. Reis remained steadfastly loyal through the transition, continuing to represent the independent Melqui Galvão Jiu-Jitsu association on the world stage. That loyalty reflects both the depth of his relationship with his coach and his identity as a competitor — one whose roots in Manaus remain central to his story, regardless of the organizational structures surrounding him.

The defining chapter of Diogo Reis's competitive career was written on the ADCC stage, where he established himself as the unambiguous master of the 66 kg division across two consecutive editions of the world's most prestigious submission grappling tournament.

At 2022 ADCC World Championship, Reis claimed gold in the 66 kg bracket, defeating a field of the sport's most accomplished no-gi grapplers and announcing himself as the division's new standard-bearer. The title was a landmark achievement at just 20 years old, validating the promise he had shown throughout his colored belt years and cementing his status as a genuine elite on the black belt circuit.

What followed was arguably even more impressive. Dedicating his 2024 competitive season exclusively to no-gi competition in order to peak at the right moment, Reis returned to the ADCC stage at 2024 ADCC World Championship and successfully defended the 66 kg title, becoming a back-to-back champion. Consecutive ADCC gold in the same division is a rare accomplishment that places a competitor in elite company — the preparation, consistency, and competitive resilience required to repeat at ADCC separates the very best from the merely excellent. His double gold run, built on a relentless wrestling base and aggressive submission hunting, confirms his place among the sport's all-time greats in the making.

In 2024, Diogo Reis extended his competitive footprint beyond the traditional tournament circuit by signing with ONE Championship to compete in submission grappling bouts broadcast to a global audience. The move brought professional jiu-jitsu to a broader fanbase and placed Reis's aggressive style under the spotlight of one of the world's largest combat sports promotions.

Promotional Debut and Injury Setback

His ONE promotional debut came against Shoya Ishiguro at ONE Fight Night 29 on March 7, 2025 — a submission grappling bout in which Reis earned an impressive victory. His involvement with ONE Championship has been entirely within the submission grappling format; he carries a 0-0-0 MMA record.

The path to ONE's flyweight submission grappling title included a significant setback. Reis had been signed to face Mikey Musumeci in what generated considerable anticipation, but a knee injury sustained during a match against a competitor known as "Pato" forced his withdrawal. Opting for conservative treatment over surgery, he committed to six months of physical therapy, used the rehabilitation period to increase muscle mass and stabilize the joint, and kept Musumeci's team informed of his unavailability. He used two ADCC matches as performance benchmarks to gauge his readiness before returning to full competition.

ONE Flyweight Submission Grappling World Championship

The return paid off decisively. On December 5, 2025, at ONE Fight Night 38, Reis faced Daiki Yonekura for the ONE Flyweight Submission Grappling World Championship at 61 kg and claimed the title with a commanding performance. The achievement added a professional promotion championship to an already decorated résumé. On January 2, 2026, ONE Championship named Reis their Submission Grappler of the Year for 2025, recognizing him as the standout performer in the discipline across the full calendar year. Reis has acknowledged interest from the UFC but stated clearly that his priority remains fulfilling his existing ONE Championship commitments.

Diogo Reis competes under the nickname "Baby Shark" — a moniker earned through his rapid ascent and the relentlessly predatory style he brings to every match. The nickname captures something essential about how he operates: once he engages, he rarely relents, hunting for finishes and maintaining pressure through every exchange.

At the technical core of his game is a wrestling-based approach to initiating and controlling matches. He moves forward consistently, uses takedowns and positional pressure to dictate where the match goes, and launches submission attempts from virtually every position. His guard passing is aggressive rather than patient, and his submission hunting reflects a willingness to accept positional trade-offs in exchange for attacking opportunities.

Reis possesses genuine versatility across formats. His gi foundation, built through years of IBJJF competition from the juvenile level onward, informs his positional understanding and technical precision. His no-gi game, sharpened through ADCC competition and ONE Championship submission grappling, reflects a more dynamic, wrestling-heavy approach suited to the faster pace of no-gi exchanges. The combination makes him dangerous in any ruleset. His willingness to compete at higher weight classes — moving up from roosterweight in gi toward featherweight divisions — further signals a competitive philosophy that prioritizes meaningful challenges over comfortable mismatches.

Alongside his submission grappling career, Reis has invested time developing the striking skills that a potential MMA transition would require. He has trained at the Fighting Nerds gym, working on his stand-up game in a structured environment that reflects a deliberate, long-term approach to broadening his combat sports skill set.

The decision to develop striking speaks to a strategic awareness of what separates submission grappling from mixed martial arts competition. Reis has shown no interest in rushing an MMA debut without proper preparation — every competitive appearance under ONE Championship has been a submission grappling bout, and no MMA debut has taken place. His acknowledgment of UFC interest, paired with his stated commitment to honoring his ONE Championship obligations first, positions any MMA transition as a future consideration rather than an immediate plan. The groundwork being laid at Fighting Nerds prepares him to make an informed, well-timed entry into MMA if he chooses to pursue it.

One of the most personally meaningful milestones of Diogo Reis's life arrived not on the competition mat but through military service. In 2023, Reis was officially inducted into the Brazilian Army as a Third Sergeant — a rank attained through a specialized program designed to allow high-performance athletes to serve their country while maintaining their competitive careers.

For Reis, the induction fulfilled a childhood dream. Wearing the army uniform had been a personal aspiration long before his grappling career took shape, lending the achievement an emotional weight that transcends sport. The dual identity — elite competitor and military serviceman — reflects the breadth of his ambitions and the seriousness with which he approaches commitments outside the gym. He balances national service obligations with an active international competition schedule, carrying the symbolic weight of representing Brazil in two distinct but complementary arenas.

Navigating weight class strategy is a persistent and complex challenge for Diogo Reis, whose competitive calendar spans multiple formats with different divisional structures. In gi competition, his primary division is roosterweight at 57.5 kg — one of the lightest and most demanding weight classes to maintain. In no-gi and submission grappling formats, he operates at heavier weights, most notably the 66 kg division at ADCC and the 61 kg flyweight division under ONE Championship's promotional structure.

The 61 kg flyweight limit for his ONE Championship appearances requires careful weight management distinct from his gi competition, and Reis has spoken publicly about the difficulty of maintaining muscle mass and strength while cutting to that figure. The knee injury sustained ahead of a planned match against Mikey Musumeci added complexity to this equation: the rehabilitation process required him to build muscle mass as part of joint stabilization, which in turn affected the baseline from which he manages his competition weight.

Looking beyond his established weight classes, Reis has announced intentions to compete at featherweight in gi competition — a step up that would place him against a different tier of opponents and test him in a new competitive context. This multi-divisional approach reflects both the practical realities of his physical development and a competitive philosophy firmly oriented toward challenge rather than comfort.