Casimiro de Nascimento Martins, better known as Rei Zulu, is a Brazilian former vale-tudo fighter that specialized in a traditional fighting style from his native Maranhão known as tarracá. Rei Zulu had been and continues to be considered a legendary figure in the MMA scene in Brazil, particularly in the vale-tudo circuit. He is also the father of MMA fighter Zuluzinho.

Vale Tudo or vale-tudo, also known as No Holds Barred (NHB) in the United States, is an unarmed, full-contact combat sport with relatively few rules. It became popular in Brazil during the 20th century and would eventually evolve into modern mixed martial arts (MMA). For years, "Vale Tudo" was used as a synonym for MMA in Brazil, but the term fell into disuse due to the emergence of stricter rules and the influence of the media to have a more "civilized" name. It is now used to refer to an early, more rules-free stage of the modern sport.