Imagawa Yoshimoto (今川 義元; 1519 – June 12, 1560) was a Japanese samurai and daimyō (feudal lord) of the Sengoku period. Based in Suruga Province, he was known as The number one archer in the Tōkaidō (海道一の弓取り, Kaidō-ichi no Yumitori); he was one of the three daimyō that dominated the Tōkaidō region. He died in 1560 while marching to Kyoto. He was killed in the village of Dengakuhazama in Okehazama by Oda Nobunaga.
Yoshimoto was born as in 1519, the third son of Imagawa Ujichika of the Imagawa clan, which claimed descent from Emperor Seiwa (850–880). His childhood name was Yosakimaru (芳菊丸). His family branched from Minamoto clan by the Ashikaga clan. As he was not the eldest son, he was not an heir to his father's lordship. As a result, the young boy was sent to a temple where his name was changed to Baigaku Shōhō (梅岳承芳) or Sengaku Shōhō (栴岳承芳).
In 1536, his older brother Ujiteru died suddenly, unleashing successional disputes. His elder half-brother, Genkō Etan (玄広恵探), tried to seize the lordship, but the clan split into two factions. Yoshimoto's faction argued he was the rightful heir because Yoshimoto's mother (Jukei-ni) was the consort of Ujichika. Genkō Etan's faction disputed this based on Genkō's seniority, and that his mother was a member of the Kushima family. However, with the assistance of Hojo Ujitsuna of Sagami province and support of Takeda Nobutora of Kai province, the Genkō faction was eliminated in the Hanagura Disturbance (花倉の乱, Hanagura-no-ran).
Baigaku Shōhō changed his name to Yoshimoto at this point and succeeded the clan.
After Yoshimoto succeeded to family headship, he married the sister of Takeda Shingen of Kai. This allowed Yoshimoto to cement an alliance with the Takeda when he helped Shingen imprison his father, Takeda Nobutora, in 1540. Soon after, the Later Hōjō clan invaded into the Suruga province but Yoshimoto defeated the Hōjō's force.
In 1542, Yoshimoto began his advance into Mikawa Province, in an effort to fight the growing influence of Oda Nobuhide in that region, but was defeated in the 1542 Battle of Azukizaka.
Later in 1548, Yoshimoto defeated Nobuhide in the Second Battle of Azukizaka and continued to expand his territory until 1560. In campaigns over the course of the ensuing decades, Yoshimoto wrested control over the Suruga, Totomi, and Mikawa provinces.
In 1552, Shingen's son, Takeda Yoshinobu, married Yoshimoto's daughter. Yoshimoto and the Hōjō clan reached a peace agreement in 1554 with the marriage of Yoshimoto's son, Imagawa Ujizane, to the daughter of Hōjō Ujiyasu, Lady Hayakawa.
In 1554, the Imagawa clan came to the west and built the Muraki Castle in the southeast of Owari, besieging Mizuno Nobumoto (uncle of Tokugawa Ieyasu) in his castle of Ogawa, who defected from the Imagawa in favor of an alliance with Oda Nobunaga.
In 1558, Yoshimoto sent Matsudaira Motoyasu to attack Terabe Castle, but were driven off by reinforcements sent by Oda Nobunaga. Later, Yoshimoto left the clan's political affairs in Ujizane's hands, in order to focus on dealing with the advance westward into Mikawa and Owari.
In the summer of 1560, after forming a three-way alliance with the Takeda and the Hōjō, Yoshimoto headed out to the capital with Matsudaira Motoyasu (later known as 'Tokugawa Ieyasu') of Mikawa in the vanguard. Despite having a strong force of 25,000, Yoshimoto deliberately announced that he had 40,000 troops. While this statement put fear in many factions, Oda Nobunaga was not dissuaded. (Some historical sources support the claim of 40,000.)
After capturing several castles from the Oda clan, Yoshimoto's army let its guard down, celebrating with song and sake. However, Oda Nobunaga launched a surprise attack with his army of 3,000 following a downpour and defeated Yoshimoto's army. Two Oda samurai (Mōri Shinsuke and Hattori Koheita) ambushed and killed Yoshimoto in the village of Dengakuhazama.
Ujizane succeeded to family headship after Yoshimoto's death, but the Imagawa clan fell from power. Ujizane was later summoned by Tokugawa Ieyasu and became a kōke in the administration of the Tokugawa clan. Yoshimoto's niece was Lady Tsukiyama, the wife of Tokugawa Ieyasu.
Yoshimoto has several graves; his body itself is buried at Daisei-ji, a temple in the city of Toyokawa in modern Aichi Prefecture.
Concubine: Ii Naohira's daughter
Chotoku Ichigetsu (d. 1625) by Jōkei-in
Reishō-in (d. 1612) married Takeda Yoshinobu by Jōkei-in
daughter married Mure Katsushige