Nagao Kagetora (長尾 景虎; February 18, 1530 – April 19, 1578), later known as Uesugi Kenshin (上杉 謙信), was a Japanese daimyō (magnate). He was born in Nagao clan, and after adoption into the Uesugi clan, ruled Echigo Province in the Sengoku period of Japan. He was one of the most powerful daimyō of the Sengoku period. Known as the "Dragon of Echigo", while chiefly remembered for his prowess on the battlefield as a military genius and war hero, Kenshin is also regarded as an extremely skillful administrator who fostered the growth of local industries and trade, as his rule saw a marked rise in the standard of living of Echigo.

Kenshin is famed for his honourable conduct, his military expertise, a long-standing rivalry with Takeda Shingen, his numerous defensive campaigns to restore order in the Kantō region as the Kanto Kanrei, and his belief in the Buddhist god of war Bishamonten. Many of his followers and others believed him to be the avatar of Bishamonten and called Kenshin the "God of War".

His original name was Nagao Kagetora (長尾景虎). He changed his name to Uesugi Masatora (上杉政虎) when he came to lead the Uesugi clan, and in order to accept the official title of Kantō Kanrei (関東管領) he changed his name again to Uesugi Terutora (上杉輝虎) to honor the 13th shōgun Ashikaga Yoshiteru (足利義輝), and finally to Kenshin (上杉謙信) after he vowed to become a Zen-Buddhist. He would become renowned for being a devotee of Bishamonten.

Kenshin was born in the Tiger year (Chinese zodiac) and always kept the word "tora" (虎, tiger) in his names. He is respected as "The Tiger of Echigo" for his intelligence and accomplishments. Kenshin is also referred to as "The Dragon of Echigo" (越後の龍) because of his Kakarimidareryuu (懸かり亂れ龍) ensign displayed on the battlefield.

His rival Takeda Shingen was called "The Tiger of Kai". They fought five times at the various Battles of Kawanakajima. In some versions of Chinese mythology (Shingen and Kenshin had always been interested in Chinese culture, especially the works of Sun Tzu), the Dragon and Tiger have always been bitter rivals who try to defeat one another, but neither is ever able to gain the upper hand. Kenshin and Shingen were also known to harbour a deep respect for the other's military prowess and strategic foresight with Kenshin even going so far as to express grief and weep at news of Shingen's death.

His ceremony of departure to war started with praying at the shrine of Bishamonten, a traditional farewell meal with the generals with three dishes (symbolizing good fortune) and three cups, which also symbolized good luck and onmyōdō's heaven, earth and man. It was followed by two shouts "Ei!" (Glory") and "O!" (Yes!) with the assembled troops, also repeated three times, and the army standard lowered to the generals as a way of respect. In the end, Kenshin re-dedicated to the war god with the "bow of Hachiman", and mounted his horse surrounded by three flag banners; first with the first character of the Bishamonten's name, second with the red rising sun on blue (Emperor's gift), and third, the warring dragon flag.

Kenshin born as Kagetora, the third or fourth son of the noted warrior Nagao Tamekage (長尾為景). His life presents a unique story – he was not from the Uesugi, but the Nagao clan. His father's family were the retainers of the Yamanouchi branch of the Uesugi clan, and his father had gained some renown with his military victories over his lords Uesugi Akisada, Uesugi Sadanori and Uesugi Funayoshi.

However, in later years, Tamekage found himself at odds with the neighboring Ikkō-ikki of Hokuriku and, as the political power in the region started to shift in favor of the Ikkō-ikki (due largely to the sudden rise of Hongan-ji), the situation for Echigo quickly deteriorated. It came to a peak in 1536, when Kenshin's father gathered up an army and marched westward. However, upon arriving at Sendanno (December 1536) in Etchū, his forces were suddenly attacked by Enami Kazuyori and in the resulting fracas Tamekage himself was slain and his army put to flight.