The Minamoto were a famous clan of warriors in medieval Japan. Their clan was also known as the "Genji," based on an alternate reading of the Chinese character for Minamoto (meaning "origin"). Hikaru Genji, the protagonist of Murasaki Shikibu's famous novel Tale of Genji, was implied to be a member of the Minamoto clan, and the Minamoto serve as the antagonists in the epic war saga Tale of the Heike.
During the Heian period, the Imperial Family started getting too large, so a series of emperors began granting some of the members of their extended family new surnames, in effect spinning them off into new families no longer part of the Imperial House. Some of these Imperial princes were given the surname "Minamoto," and others were given the name "Taira." This was the origin of the mighty Minamoto and Taira clans who would gain increasing power through their control of armies of mounted warriors, who would later come to be known as "samurai." Contention between these two clans would ultimately lead to the climactic Gempei Civil War (the basis of the Tale of the Heike), which would bring an end to the golden age of the Heian period, and lead to a shifting of power away from the courtiers in Kyoto and into the hands of warrior shoguns.
The first members of the Minamoto clan were given the surname "Minamoto" by Emperor Saga starting in the year 814. Famous Minamoto include Minamoto Yoshitomo, Minamoto Sanetomo, Minamoto Yoshitsune, and Minamoto Yoritomo, the victor in the Gempei War and the founder of the Kamakura Shogunate.