Ishida Mitsunari (石田 三成, 1559 – November 6, 1600) was a Japanese samurai and military commander of the late Sengoku period of Japan.

Mitsunari was born in 1559 at the north of Ōmi Province (which is now Nagahama city, Shiga Prefecture), and was the second son of Ishida Masatsugu, who was a retainer for the Azai clan.

According to the "Hitotsuyanagi Kaki", he was in charge of a mission to spy on Shibata Katsuie's army and also performed a great feat of Ichiban-yari (being the first to thrust a spear at an enemy soldier) as one of the warriors on the front line.

He was appointed one of the five bugyō, or top administrators of Hideyoshi's government, along with Asano Nagamasa, Maeda Gen'i, Mashita Nagamori and Natsuka Masaie.

[citation needed] In 1588, Mitsunari was placed in charge of the famed “sword hunt” conducted by Hideyoshi in an effort to disarm the non-military bulk of the population and preserve peace.

However, Mitsunari was on bad terms with some daimyō that were known as good warriors, including Kuroda Nagamasa and Hachisuka Iemasa, as well as Hideyoshi's nephew Kobayakawa Hideaki.

The central point of the conflict was the question of whether Tokugawa Ieyasu could be relied on as a supporter of the Toyotomi government, whose nominal lord was still a child, with actual leadership falling to a council of regents.

After the death of the respected "neutral" Maeda Toshiie in 1599, the conflict came to arms, with Mitsunari forming an alliance of Toyotomi loyalists to stand against Tokugawa Ieyasu.

[citation needed] A legend says that Ieyasu showed him mercy but hid him, for political reasons, with one of his veteran generals, Sakakibara Yasumasa, where he grew old and died of natural causes.

To thank Yasumasa for his silence, Mitsunari gave him a tantō nicknamed Ishida Sadamune (石田貞宗) – a National Treasure of Japan.

[citation needed] Mitsunari had three sons (Shigeie, Shigenari, and Sakichi) and three daughters (only the younger girl's name is known, Tatsuhime) with his wife.

[5] Stephen Turnbull stated that traditional Japanese historiography did not pay much attention to Mitsunari's legacy, as he lost and Tokugawa won; he was often portrayed as a weak bureaucrat.

His reputation has somewhat recovered since then, with later historians note his skill in planning and earlier battlefield victories, and that Sekigahara could easily have gone his way had a few more lords remained loyal.

[1] According to popular theory, in 1598, after the death of Toyotomi Hideyoshi, the government of Japan had an accident when seven military generals consisting of Fukushima Masanori, Katō Kiyomasa, Ikeda Terumasa, Hosokawa Tadaoki, Asano Yoshinaga, Katō Yoshiaki, and Kuroda Nagamasa planned a conspiracy to kill Ishida Mitsunari.

However, Mitsunari had learned of this from a report by a servant of Toyotomi Hideyori named Jiemon Kuwajima, and fled to Satake Yoshinobu's mansion together with Shima Sakon and others to hide.

Ieyasu then negotiated a promise to let Mitsunari retire and to review the assessment of the Battle of Ulsan Castle in Korea which had been a major source of this incident.

[6][11] Muramatsu Shunkichi, writer of "The Surprising Colors and Desires of the Heroes of Japanese History and violent women”, gave his assessment that the reason of Mitsunari failed in his war against Ieyasu was due to his unpopularity among the major political figures of that time.

However, this view was challenged by Tonooka Shin'ichirō, a professor at Nara University and director of the Tsuruga City museum, as Shin'ichirō viewed the political maneuvers which led to the conflict in Sekigahara as being solely based on Mitsunari's motivation to regain his political position after the coup of military factions which stripped him of his position and had nothing to do with Ieyasu at personal level.