The Mandalorians (25,053 BBY - 738 BBY)

"Here's why you can't exterminate us, aruetii.  We're not huddled in one place - we span the galaxy.  We need no lords or leaders - so you can't destroy our command.  We can live without technology - so we can fight with our bare hands.  We have no species or bloodline - so we can rebuild our ranks with others who want to join us.  We're more than just a people or an army, aruetti.  We're a culture.  We're an idea.  And you can't kill ideas - but we can certainly kill you."

- Mandalore the Destroyer

History
The Mandalorians - known in Mando'a as the Mando'ade, or "Children of Mandalore" - were a nomadic group of clan-based people consisting of members from multiple species and multiple genders, all bound by a common culture.

In their early years, Mandalorian culture revolved around battle, with war being a source of honor and pride in their community. The leader of the Mandalorians was known as the Mand'alor, translating to "Sole Ruler" and was rendered as "Mandalore" in Basic. Throughout their history, the Mandalorians were frequently allied with the Sith, perhaps most notably the Sith Lord Exar Kun, and held a certain distrust and general dislike for the Jedi Order. However, they would not hesitated to cooperate with the Jedi if a partnership between the two groups was mutually beneficial. In later years, the Mandalorians moved away from their obsessively war-like and conqueror ways and instead, most became bounty hunters and mercenaries, selling their skills to various individuals and factions in the galaxy. However, the Mandalorian Protectors sided with the Alliance to Restore the Republic ever since about 3 ABY and even continued to serve the Alliance of Free Planets, the New Republic, and finally the Galactic Alliance.

When Boba Fett took the title of Mandalore years later, they were approached by the powerful unknown empire of the Yuuzhan Vong to aid them as wealthy mercenaries, and while the offer was accepted (mainly because the other option would have been the enslavement of the Mandalorian homeworld), Boba managed to feed information to the New Republic, and while the Mandalorians continued to fight for the Vong in the early Yuuzhan Vong War, they soon betrayed them and fought with the many other factions defending the galaxy. After the war ended, the Second Galactic Civil War began, and Jaina Solo, daughter of Han and Leia, came to Fett asking to be trained, given the Mandalorians' famous reputation as legendary warriors against the Jedi. The Mandalorians ironically fought alongside the New Jedi Order, their former enemies in the crusades many years before and the Alliance-in-exile in this conflict. With training from Fett, and from others, Jaina killed her brother Darth Caedus, ending the war. Ultimately, in the span of over four thousand years, Mandalorians slowly changed from the feared Mandalorian Crusaders of the Sith Empires, to the elite soldiers of the Jedi Coalition and later the reorganized Galactic Alliance, fighting for a cause rather than mainly for credits and the destruction of worlds.

Mandalorians wore very distinctive battle armor, including helmets with T-shaped visors that covered the entirety of their faces, and would provide inspiration for the helmets of the Republic's clone troopers. These helmets would eventually become strongly associated with the Mandalorian people.