was a Japanese samurai of the late Edo period, feared as one of the four most notable assassins of the Bakumatsu period. He was a member of (Tosa Imperialism party, a loyalist clique of Tosa) in his hometown, Tosa Domain. Izà  and Tanaka Shinbei were active in Kyoto as assassins under the leadership of Takechi Hanpeita.
His personal name () was Yoshifuru.
Okada Izà  was born in Iwamura, Kami, Tosa as the eldest son of a country samurai Okada Yoshihira. He had a younger brother named Okada Keikichi who also joined the Kinnoto.
First self-taught in swordplay, Okada later became a pupil of Takechi Hanpeita under Nakanishi-ha Ittà Â-ryà « (ä¸Â西派ä¸ÂÃ¥ÂÂæµÂ) school, a branch of school. Following Takechi, in September 1856 Okada went to Edo and studied at Shigakukan, which was the training hall of Momonoi Shunzà Â. He returned to Tosa the following year.
In 1860, Okada followed Takechi and practiced martial arts in Chà «goku and Kyushu regions. Takechi considered that house of Okada would have difficulties with covering travel expenses and so asked the feudal lord of Oka domain in Bungo province to accommodate his student. In Oka, Izà  studied school of kendo. Around May 1861, he left to Edo and returned to Tosa in April of the following year. The same year he joined Tosa Kinnoto, organized by Takechi and loyal to the Sonnà  Jà Âi movement. For some reason however, he was later crossed off from the name list, along with and å¼Âç°æÂÂå©.
Starting with Inoue Saichiro, who was the shita metsuke (low class inspector of foot soldiers) of the Tosa Domain, Izà  assassinated Honma Seiichiro who was his comrade, Ikeuchi Daigaku, Mori Magoroku, Ogawara Juzo, Watanabe Kinzan, and Ueda Jonosuke, who were government officials and yoriki (police sergeants) that belonged to the Kyoto City Magistrate, Tada Tatewaki (son of Nagano Shuzen who commanded Ansei no Taigoku [suppression of extremists by the Shogunate] and Murayama Kazue, who during the assassination was tied to a bridge and made a public display alive). Those killings were conducted in the name of "Heaven's punishment" (天誠, Tenchà «), as Takechi called it. Izà  became known as 'Hitokiri (man-slayer) Izà Â' and feared, with a fellow hitokiri Tanaka Shinbei of Satsuma Province.
Izà  later worked as a bodyguard; in 1863 Izà Â, owing to the mediation of Sakamoto Ryà Âma, was hired by Katsu Kaishu. Three assassins attacked Kaishu, but when Izà  cut one of them down and gave a roar, the remaining two assassins ran away. Katsu, confident in Izà Â's skill as his own bodyguard, made him become a bodyguard of Nakahama Manjirà Â. When they went to a western style grave that Manjirà  had built, four assassins tried to attack Manjirà Â, but Izà  had sensed the two ambushes that were hiding, and told Manjirà  not to escape impulsively but to stay put with his back against the gravestone, and slew the two attackers down. The remaining two attackers made an escape.
After the Coup of August 18 in 1863, the Kinnoto lost its momentum. Around June 1864, he was captured by a shogunate official, and on the charge of being tattooed, he was banished from the capital Kyoto; at the same time, an official of the Tosa Domain captured him, and deported him to his hometown.
In 1865 however, he was involved in yet another assassination, that of Yoshida Tà Âyà Â, the regent of Tosa whom he killed before his rise to power. In the Tosa Domain, all his comrades of the Tosa Kinnoto were arrested for that assassination and the series of assassinations that took place in the capital Kyoto. With the exception of Takechi, who was a Joshi (superior warrior) rank, they all underwent severe torture. Takechi, who learned of Izà Â's arrest, wrote in a letter to his home, 'it is better for such a fool to die soon, and how his parents would lament over him for returning unashamedly to his hometown,â which indicates his ill feeling towards Izà Â. Letters which were considered to be written by Tauchi Keikichi (TakechiâÂÂs real younger brother) and so on tell that since his house stood in Shichiken machi, Izà  was also disdainfully referred to as 'ä¸Â以.â On learning of Izà Â's arrest, some comrades both in and out of prison, including the Yamauchi family who was behind Yoshida's assassination, became afraid that Izà Â's confession may put them on line, and planned to poison Izà Â; however, Takechi successfully argued against the plan. Izà  endured severe torture, but he finally made a full confession and was beheaded on May 11, 1865, and his head was put on public display.
His death poem read 'My mind that served for you came to nothing, and will only clear up after you've gone.' (Ã¥ÂÂãÂÂçº å°½ãÂÂå¿Â㯠水ã®泡 æ¶Âã«ãÂÂã®ã¡ã ãÂÂã¿渡ãÂÂã¹ãÂÂ)
His grave is the family grave in the mountains near Azo Station at KÃ Âchi City, KÃ Âchi Prefecture. He was buried under his personal name, Okada Yoshifuru.
There are some photographs passed around as photos of Izà Â, but most of them show and . There are no known photographs of actual Izà Â.
Several films feature Okada Izà  as protagonist, most notably Hideo Gosha's Hitokiri (1969) (portrayed by Shintaro Katsu) and Takashi Miike's Izo (2004) (portrayed by Kazuya Nakayama). The NHK Taiga drama Ryà Âmaden (2009) featured him several times (portrayed by Takeru Sato) as one of Sakamoto Ryà Âma's friends and Takechi Hanpeita's assassins.
In manga, Nobuhiro Watsuki based the character Kurogasa Udà  Jin-e of his series Rurouni Kenshin on Izà Â; the author admits that the character bears little resemblance to Izà Â. Hideaki Sorachi also based Nizo Okada, a character in his work Gintama, on Izà Â. Masami Kurumada, author of the popular Saint Seiya manga series, more recently added a character to his work, called Capricorn Izà Â, who is inspired by Okada. The manga Assassin by Hiroshi Hirata is based on the same story depicted in the film Hitokiri.
In the video game Way of the Samurai 4, one of the characters, Kogure, may be inspired by Izà  Okada.
Okada also appeared in Kengo, a video game based on nine legendary swordsmen. In the game, his full name is revealed to be Okada Izà  Nobutoshi and it is explained he uses a Goken style of swordsmanship, meaning to overpower the opponent through physical strength and audacious assaults, much like the Jigen-ryu used by some other hitokiri of the Bakumatsu period.
Okada appears as a character in the 2014 video game ', as well as its 2023 remake, bearing similarities with Yakuza series character Akira Nishikiyama.
In 2018 he appeared in the mobile game Fate/Grand Order as an Assassin-class Servant.
Okada appears as a character in the 2024 video game "Rise of the RÃ Ânin". His name is done as Izo Okada.