The Ikedaya Jiken (池田屋事件), also known as the Ikedaya Affair, was a famous armed encounter between the anti-shogunate forces from Choshu (now Yamaguchi) and the Shinsengumi in July 1864 in Kyoto, Japan. The anti-shogunate forces were planning to set fire in Kyoto and overthrow the Aizu clan who were policing Kyoto at the time. The Shinsengumi discovered their plan and slaughtered them before they could carry it out, losing only one of their number in the process. This incident made it clear in Kyoto that the Shinsengumi were a powerful force to be feared by the anti-shogunate.