Samurai were a warrior class that existed in ancient and feudal Japan.

One such knight of this warrior class ambushed Hikaru Sulu. While on the Amusement Park planet, Sulu's sub-conscious mind summoned one. Forced to flee, as his phaser was inoperable, Sulu escaped from the katana blade the samurai wielded. (TOS episode: "Shore Leave")

Illusions of Hikaru Sulu and a Samurai fought with Katanas after being discussed by James T. Kirk and Doctor Leonard McCoy. (TOS comic: "The Tree of Life, the Branches of Heaven")

They were also the name of the group of warriors in the Mirror Universe that served under Emperor James T. Kirk. They were completely loyal to their leader and would obey orders-even if it meant their death. They wore black versions of Cardassian battle armor with red sashes that signified the blood they had sworn to their leader.

It is not known if this class of warriors existed solely under Kirk or if they were already present within the Terran Empire, considering its altered militaristic nature. (TOS novel: Dark Victory)