Uesugi Kenshin (上杉 謙信^?, February 18, 1530 – April 19, 1578) was a daimyo who ruled Echigo province in the Sengoku period of Japan.

He was one of the many powerful lords of the Sengoku period. He is famed for his prowess on the battlefield, the legendary rivalry with Takeda Shingen, his military expertise, strategy and his belief in the Buddhist god of war — Bishamonten. In fact, many of his followers and others believed him to be the avatar of Bishamonten, and called Kenshin 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 inherited the Uesugi family name in order to accept the official title of Kantō Kanrei (関東管領). Later he changed his name again to Uesugi Terutora (上杉輝虎) to honor the Shogun Ashikaga Yoshiteru (足利義輝), and finally to Kenshin (上杉謙信) after he became a Buddhist monk; in particular, he would become renowned for being a devotee of Bishamonten. For the majority of this biography, the name of Kenshin will be used. Kenshin is sometimes referred to as "The Dragon of Echigo" because of his fearsome skills in the martial arts displayed on the battlefield. His rival Takeda Shingen was called "The Tiger of Kai". 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.

Born the fourth son of the noted warrior Nagao Tamekage (長 尾為景), Kenshin's early life presents a unique story. His father had gained some renown as a warlord through his military victories over 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 (due largely to the sudden rise of the Honganji), the situation for Echigo quickly deteriorated. It came to a peak in 1536, when Kenshin's father gathered up an army and marched westward, his aim uncertain. However, upon arriving at Sendanno in Etchu, his forces were suddenly attacked by Enami Kazuyori, and in the resulting battle Tamekage himself was slain, and his army put to flight.

The impact back at Echigo was immediate. Nagao Harukage, Tamekage's eldest son, immediately made his bid for control of the Nagao, and succeeded in this claim after a power struggle which resulted in the death of one of his brothers, Kageyasu. Kagetora (Kenshin) was removed from the conflict and relocated to Rizen temple, where he spent his life from 7 to 14 dedicated to study.

At the age of fourteen, Kenshin was suddenly contacted by Usami Sadamitsu and a number of other acquaintances of his late father. They urged the young Nagao son to go to Echigo and contest his older brother's rule. It would seem that Harukage hadn't proven the most effective or inspiring leader, and his failure to exert control over the powerful kokujin families had resulted in a situation which was nearly to the point of tearing the province apart.

As the story is told, at first Kenshin was reluctant to take the field against his own brother, but was eventually convinced that it was necessary to the survival of Echigo. In a series of engagements led by himself and Usami Sadamitsu, Kenshin succeeded in wresting control of the clan from Harukage in 1547. Harukage's own fate is uncertain, as some sources claim he was allowed to live, but others record his forced suicide.

Though his rule over the Nagao clan was now unquestioned, much of Echigo was still independent of this young warlord's grasp. Kenshin immediately set out to cement his power in the region, but these efforts were still in their infant stages when far more pressing concerns appeared. Ogasawara Nagatoki and Murakami Yoshikiyo, two Shinano lords, both appeared before Kenshin requesting his help in halting the advances of the powerful warlord Takeda Shingen. Around the time Kenshin became the new lord of Echigo, Shingen had won major victories in Shinano Province. With the Takeda's conquests taking them remarkably close to the borders of Echigo, Kenshin agreed to take the field.

What followed was the beginning of a rivalry which became legendary. In the first conflict between the two, both Uesugi Kenshin and Takeda Shingen were very cautious, only committing themselves to indecisive skirmishes. Over the years, there would eventually be a total number of five such engagements at the famous site of Kawanakajima, though only the fourth would prove to be a serious, all-out battle between the two.

In 1561, Kenshin and Shingen fought the biggest battle they would fight, the fourth battle of Kawanakajima. Kenshin used an ingenious tactic: a special formation where the soldiers in the front would switch with their comrades in the rear, as those in the frontline became tired or wounded. This allowed the tired soldiers to take a break, while the soldiers who had not seen action would fight on the frontlines. This was extremely effective and because of this Kenshin nearly defeated Shingen. In this battle is the tale of Kenshin riding up to Shingen and slashing at him with his sword. Shingen fended off the blows with his iron war fan or tessen. However, Kenshin failed to finish Shingen off. A Takeda retainer drove him away, and Shingen made a counter attack. The Uesugi army retreated and many drowned in a nearby river while others were cut down by the Takeda.

The result of the fourth battle of Kawanakajima is still uncertain. Many scholars are divided on who the actual victor was, if the battle was actually decisive enough to even declare one. Kenshin lost 3000 of his army while Shingen lost around 4000, but Shingen also lost two of his most important generals during the battle, namely his advisor Yamamoto Kansuke and younger brother Takeda Nobushige.

Although Shingen and Kenshin were rivals for more than fourteen years, they are known to have exchanged gifts a number of times, most famously when Shingen gave away a precious sword, which he valued greatly, to Kenshin. Shingen died in 1573, and Kenshin was said to have wept aloud at the loss of so worthy an adversary, and reportedly vowed to never attack Takeda lands. The two sides became allies in 3 years. In addition, there was an incident when a number of other daimyo (including the Hōjō clan) boycotted salt supplies to Kai province. Kenshin heard of Shingen's problem with a daimyo of the Hōjō clan who refused to send rice to him. Kenshin secretly sent salt to the Takeda (salt was a precious commodity as it was used in preserving food) and wrote to his enemy, Shingen, that in his opinion, the Hōjō lord had committed a hostile act. Although he could have cut off Shingen's supplies and "lifeline", Kenshin decided not to do so because it would be dishonorable. In reflection, Kenshin made a statement "Wars are to be won with swords and spears, not with rice and salt." In this, Kenshin set a noble example for all time in his treatment of his rival Shingen. The statement is a common modern reference by peace advocates who in recognition of Kenshin state that "peace is to be achieved with rice and salt, not with swords and spears".

Though his rivalry with Takeda Shingen was legendary, Uesugi Kenshin actually had a number of other ventures occurring around the times of these famous battles (1553, 1555, 1557, 1561, 1564). In the year 1551, Kenshin was called upon to provide refuge for his nominal lord, Uesugi Norimasa, who had been forced to flee there due to the expansion into the Kantō by the Hōjō clan. Kenshin agreed to give the warlord shelter, but was not in a position at the time to move against the Hōjō. In the year 1559, he made a trip to pay homage to the shogun in Kyoto, and visited many religious and historical sites in the area. This served to heighten his reputation considerably, and added to his image as a cultured leader as well as a warlord. This same year he was pushed once again by Uesugi Norimasa to take control of the Kantō back from the Hōjō, and in 1560 he was able to comply. Heading a campaign against the Hōjō, Kenshin was successful in taking a number of castles from the clan, which ended in his striking against the Odawara Castle in Sagami Province. He managed to break the defenses and burn the town, but the castle itself remained unconquered, and lack of supplies forced his retreat soon after. However, it was during this time that he visited the Tsurugaoka Hachiman-gū and took the name Uesugi.

The other main area which interested Uesugi Kenshin was Etchu Province, and Kenshin would spend nearly half his life involved in the politics of that province. The land was inhabited by two feuding clans, the Jinbo and the Shiina. Kenshin first entered the dispute as a mediator in the early 1550's between rivals Shiina Yasutane and Jinbo Nagamoto, but he later sided with the Shiina and took over the Jinbo clan. Decades later, Kenshin turned against the Shiina clan, taking their main castle in 1575 and having Shiina Yasutane assassinated in 1576 by Kojima Motoshige. At this point, Etchu Province was effectively under his control.

Starting in the year 1576, Kenshin began to consider the issue of Oda Nobunaga, who had since grown to be Japan's most powerful warlord of the time. With both Takeda Shingen and Hōjō Ujiyasu dead, Kenshin was no longer blocked off from this realm of expansion. So, when the death of a Noto lord in the area sparked up confusion and conflict, Kenshin was quick to use the opportunity, taking land from the weakened clan which put him in a position to threaten Nobunaga and his allies. In response, Nobunaga pulled together his own forces and those of his two best generals; Shibata Katsuie (柴田勝家) and Maeda Toshiie (前田利家) to meet Kenshin at Tedorigawa. The experienced Shibata Katsuie who served Nobunaga since the beginning, was sent forth to test Kenshin's famed battle reputation. According to some accounts, Shibata led 18,000 men into battle first, and Nobunaga himself followed up with 20,000 reinforcements. If this information is accurate, it would make the battle between the two one of the largest fought in the Sengoku period.

Despite Nobunaga's overwhelming numbers, Kenshin managed to score a solid victory on the field. At first, Kenshin refused to engage the Nobunaga army until a heavy rainfall which neutralized Nobunaga's infantry units. Forced to make a hasty retreat, Shibata regrouped with Nobunaga's main force. Next Kenshin took a page from his old rival Takeda Shingen; he pretended to send forth a small unit to attack Nobunaga's main force from behind and gave his enemy a great opportunity to crush his remaining force. Nobunaga took the bait. Nobunaga's force attacked at night expecting a weakened opponent; instead Kenshin's full military might was waiting. After losing almost a quarter of his force, Nobunaga pulled back to Ōmi Province while Kenshin contented himself with building a few forts in Kaga Province before returning back to Echigo province. In the winter of 1577 - 1578, Uesugi Kenshin arranged to put forth a grand army to continue his assaults into Nobunaga's land. However, he was reported to be in horrid health during this time, and on April 9 he suffered a type of seizure. He died four days later.

His death poem was 「四十九年一睡の夢 一期の栄華一盃の酒」。 "Forty Nine Years; One night's dream. A lifetime of prosperity; a cup of sake." (These 49 years of my life have passed like one night's dream. My life has been full of glory and prosperity, like a single cup filled with sake.)

The cause of Kenshin's death has been questioned throughout the years. The theory accepted by most Japanese scholars is that a lifetime of heavy drinking and perhaps stomach cancer spelled the end for the great warlord. Other sources hold that he was assassinated by a ninja who had been waiting in the cess pool beneath the latrine at Kenshin's camp with a short spear. (Note that the theories are not mutually exclusive — the assassin, if he existed, might simply have fatally wounded an already dying man.) It is said that upon hearing of Kenshin's death, Oda Nobunaga remarked, "Now the empire is mine."

Kenshin's death was disastrous for the clan. He never had any sons but adopted two boys to be his heirs. Upon their adopted father's death, the two immediately entered into a power struggle, which ended with Uesugi Kagekatsu being the clan's new ruler. However, the internal struggle had cost them too much time and energy, and Oda Nobunaga had no problem taking over the majority of their lands quickly, going right up to the border of Echigo. Speculation that Kenshin was a woman posing as a man (due to the fact he did not marry) is a modern concept not considered relevant by serious scholars.