Jango Fett was a renowned Mandalorian bounty hunter, assassin, mercenary, and the "father" of Boba Fett, a genetic clone of his, whom he raised as a son. A Human from Concord Dawn, Fett was adopted by Mandalorian warriors following the murder of his parents and the disappearance of his older sister Arla in 58 BBY. Years later, he would go on to lead them through much of the Mandalorian Civil War as Mandalore. After being imprisoned by Jedi, Fett was responsible for destroying the Death Watch, a Mandalorian group who killed Fett's mentor, Jaster Mereel.
Following the conclusion of that conflict, Fett became a bounty hunter, quickly establishing a reputation as being one of the best in the galaxy. Later on, Fett agreed to serve as the genetic template for the clones that would form the bulk of the Grand Army of the Republic during the Clone Wars. When Master Obi-Wan Kenobi located Jango and Boba on Kamino, Fett fled to join Count Dooku. Though struck down by Mace Windu in combat, Fett's legacy would live on through his son Boba, as well as his cloned brethren, who would have a profound impact on galactic history.
Source: Star Wars Wikia, "Jango Fett", available under the CC-BY-SA License.