The Ishiyama Hongan-ji War was a ten-year military campaign that took place from 1570 to 1580 in Sengoku period Japan, carried out by lord Oda Nobunaga against a network of fortifications, temples, and communities belonging to the Ikkō-ikki, a powerful faction of Jōdo Shinshū Buddhist monks and peasants opposed to the rule of the samurai class.

The Sengoku period, also known as Sengoku Jidai is the period in Japanese history in which civil wars and social upheavals took place almost continuously in the 15th and 16th centuries. Although the Kyōtoku incident (1454), Ōnin War (1467) or Meiō incident (1493) are generally chosen as the Sengoku period's start date, there are many competing historiographies for its end date, ranging from 1568, the date of Oda Nobunaga's march on Kyoto, to the suppression of the Shimabara Rebellion in 1638, deep into what is traditionally considered the Edo period. Regardless of the dates chosen, the Sengoku period overlaps substantially with the Muromachi period (1336–1573).