This is a list of Samurai Jack characters. In the series, Jack is thrown into a dystopic world ruled by his enemy Aku. The setting rails from futuristic towns and mega-cities to beautiful wilderness, with a colorful number of characters from varying settings, including mutants, aliens, bounty hunters and even demonic and mythological figures.

Samurai Jack (voiced by Phil LaMarr)^[1] is the titular protagonist of the series. "Jack" (real name unknown)^{[a 1]} is the alias adopted by a Japanese imperial prince and samurai warrior, son of the Emperor who once defeated and imprisoned the demon sorcerer Aku. After Aku returns during Jack's childhood to take over all of Japan and hold the Emperor hostage, thus forcing a young Jack to flee into exile when he was still a little boy. After spending the remainder of his formative years traveling around the world to receive combat training and eventually reclaim his father's magical katana sword (Aku's sole weakness), Jack returns home as a young man to fight and destroy Aku.

But before Jack could strike the final killing blow, Aku opened a portal through time which teleported Jack into the far future, a violently dystopian world where Aku is the tyrannical emperor of Earth and the rest of the galaxy. Jack spends the rest of the series traveling around on one adventure to the next, searching for ways to time-travel back to the past to resume his goal of slaying Aku and preventing this future from ever happening. Despite numerous setbacks including the temporary loss of his sword and lack of any functional time portals to use, by the final episode Jack returns home to the past and successfully vanquishes Aku once and for all.

Aku (voiced by Mako Iwamatsu in Seasons 1 to 4, and Greg Baldwin in Season 5) is a powerful demon who destroys everything good around him, able to shapeshift and unable to be harmed by mortal weapons. As revealed in the 2-part "The Birth of Evil", Aku was a surviving fragment of a formless primordial that was destroyed by the gods Odin, Ra, and Rama. The fragment drifted across the cosmos until it crashed down on the area of Earth that would become Japan, wiping out the dinosaurs in that area while forming an lake of blackness from which an ever-spreading forest of black spikes grows around. Eventually, the Damiyo of the land (Jack's father), decided to kill the evil at its source. But the magic oil given to him by Buddhist monks gave the evil sentience as it manifested itself as Aku. But the daimyo received the gods' aid that they provide him with a katana powered by pure goodness that can harm Aku's body, the daimyo using it to seal Aku away. This imprisonment lasted less than a decade however, as a solar eclipse released Aku upon the world once more. But daimyo was prepared and sent his son to be trained by numerous cultures before returning to finish what he began. However, Aku used his power to sent the samurai into the distant future where he had long conquered Earth.

Aku constantly antagonizes Jack, often attacking him while he is weak, and other times defending himself from Jack's own gambits while thwarting every attempt he makes of returning to his time. The two seem doomed never to defeat each other, something which Aku realized by season five upon learning his magic rendered Jack unable to age. This resulted in Aku suffering melancholy. While he is usually presented as an embodiment of pure evil, Aku is also a source of comedy due to his outrageous design and sometimes wise-guy behavior.

The Emperor (voiced by Sab Shimono (older) and Keone Young (young)) is Jack's father, and the ruler of Japan. Like his son, he is a brave and heroic warrior. He was the original owner of the magic katana sword, which he used to defeat Aku during the demon's first rampage.

The Empress (voiced by Lauren Tom) is Jack's mother and the Emperor's wife.

Only known as the Scotsman (voiced by John DiMaggio), he is one of Jack's most occurring allies and an enemy of Aku. Compared to Jack, the Scotsman is boisterous and carries a two-handed Scottish claymore inscribed with Celtic runes along with grenades stored in his kilt. The Scotsman first met Jack on a days-long rope bridge, making fun of Jack's appearance before engaging him in a swordfight before they were set upon by Aku's bounty hunters. The two defeated their pursuers with the Scotsman recognizing Jack's valor, later seeking his help in saving his wife, whom he saw as dainty and beautiful, from Celtic. In the two-part "The Scotsman saves Jack", the Scotsman encounters Jack when he loses his memory to the Sirens whose song didn't effect him due to his backwards sense of beauty. Once Jack regained his memories, the two of them engaged in a series of contests with Jack winning as he rowed them back to the mainland.

In the fifth season, revealed to have fathered an army of daughters, an aged Scotsman died covering for his children when an attempted attack on Aku's stronghold failed. However, the magic in the Scotsman's sword brought him back as a spirit.

Ashi (voiced by Tara Strong) is a recurring character introduced in Season 5. Born in a set of identical septuplets, Ashi and her sisters were raised by a cult known as the Daughters of Aku for the purpose to kill Samurai Jack. The struggle that followed ended with Ashi the sole surviving sister while she eventually begins to question the ideology she was raised under, finally accepting the truth that Aku is the real enemy to the world.