The Keian Uprising (慶安事件 Keian Jiken?) was a failed coup d'état attempt carried out against the Tokugawa shogunate of Japan in 1651, by a number of rōnin. Though it failed, the event is historically significant as an indication of a wider problem of disgruntled ronin throughout the country at the time. Masterminded by Yui Shōsetsu and Marubashi Chūya, the uprising is named after the Keian era in which it took place.
According to strategist Yui's plan, Marubashi would take Edo Castle, the headquarters of the shogunate, using barrels of gunpowder to begin a fire which would rage through Edo, the capital. In the confusion, with the authorities distracted by firefighting efforts, the ronin would storm the castle and kill key high officials.
At the same time, Yui would lead a second group and seize the Tokugawa stronghold in Sunpu (modern-day city of Shizuoka). Further action was planned for Osaka Castle and Kyoto. They timed their rebellion to take advantage of the death of Shogun Tokugawa Iemitsu, as his successor, Ietsuna, was still a child. The conspirators aimed to force the shogunate to relax its policies of seizing hans and dispossessing daimyōs, which under Iemitsu had deprived tens of thousands of samurai of position and income, adding them to the ranks of ronin.