The Missoula Floods refer to the catastrophic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age.

The floods were the result of the periodic sudden rupture of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each rupture of the ice dam, the waters of the lake would rush down the Clark Fork and the Columbia River, inundating much of eastern Washington and the Willamette Valley in western Oregon. After the rupture, the ice would reform, recreating Glacial Lake Missoula once again.

Geologists estimate that the cycle of flooding and reformation of the lake lasted on average of 55 years and that the floods occurred approximately 40 times over the 2,000 year period between 15,000 and 13,000 years ago.