Brazilian jiu-jitsu (Portuguese: jiu-jitsu brasileiro [ʒiw ˈʒitsu bɾaziˈlejɾu, ʒu -]), often abbreviated to BJJ, is a self-defense system, martial art, and combat sport based on grappling, ground fighting, and submission holds. It is primarily a ground-based fighting style and focuses on taking one's opponent down to the ground, gaining a dominant position, and using a number of techniques to force them into submission via joint locks, chokeholds, or compression locks. It has its roots in jujutsu, judo and catch wrestling.

Brazilian jiu-jitsu was first developed around 1925 by Brazilian brothers Carlos, Oswaldo, Gastão Jr., and Hélio Gracie, after Carlos was taught jujutsu and catch wrestling in 1917 by either Mitsuyo Maeda, a travelling Japanese judoka, or one of Maeda's students Jacyntho Ferro. Later, the Gracie family developed their own self-defense system that they named Gracie jiu-jitsu. BJJ eventually came to be its own defined combat sport through the innovations, practices, and adaptation of Gracie jiu-jitsu and judo, and has become one of the essential martial arts for modern mixed martial arts.

Brazilian jiu-jitsu revolves around the concept that a smaller, weaker person can successfully defend themselves against a bigger, stronger opponent by using leverage and weight distribution, taking the fight to the ground and using a number of holds and submissions to defeat them. Sparring, commonly referred to as "rolling" within the BJJ community, and live drilling plays a major role in the practitioner's development. In contrast to some other martial arts BJJ can be practiced both using a gi uniform or not which is known as 'no-gi BJJ'; for this purpose rash guards are used. BJJ can also be used as a method of promoting physical fitness, building character, and as a way of life.

The first public demonstration of jiu-jitsu in Brazil took place in 1906 in the city of Manaus, the capital of Amazonas. In November of that year, the ship Jerome docked in Manaus, carrying two Japanese martial artists who were touring the Americas to showcase their fighting style: jiu-jitsu master Akishima Sadashi and his assistant Suiotos Ki.

After settling in the city, the two men published a challenge in the local newspapers, inviting anyone willing to face them in public matches. An improvised arena was set up at the "Coliseu Metálico Brasileiro" circus in Praça da Saudade, where on November 18, Master Akishima and his disciple Suiotos fought over a dozen local challengers—defeating all of them in less than five minutes each, in front of a large crowd. This marked the first official jiu-jitsu matches on Brazilian soil.

After several months of exhibitions at the circus, Akishima and Suiotos left Amazonas and sailed to Liverpool, England, aboard the ship Antony.

In 1908, the Brazilian Navy ship Benjamin Constant rescued a group of castaways on a Pacific island, among them a Japanese jiu-jitsu instructor Sada Miyako. He and his disciple Kakiara were allowed to stay aboard and continue the journey to Brazil. During the voyage, the two Japanese men taught jiu-jitsu techniques to the sailors.

Upon arriving in Rio de Janeiro aboard the Benjamin Constant, Miyako was hired by the Navy to train officers at Fortaleza de Villegagnon, later extending his teachings to Army personnel. He remained in Brazil for some time, giving private lessons, performing demonstrations, and engaging in public fights—most notably his 1909 match against capoeirista Ciríaco da Silva, which became legendary.