The Tōhoku earthquake and tsunami on March 11, 2011, resulted in three nuclear meltdowns and multiple hydrogen explosions at the Fukushima Daiichi Nuclear Power Plant in Japan.

In all of history, only two events have been designated "level 7" nuclear accidents, the classification used by the International Atomic Energy Agency (IAEA) for major events with widespread health and environmental effects. Fukushima was one of them.