Big Lou is a mountain summit located in Chelan County of Washington state. It is situated west-northwest of Leavenworth, on the boundary of the Alpine Lakes Wilderness, and on land managed by Okanogan-Wenatchee National Forest. Big Lou is the highest point on Icicle Ridge, and is the third-highest peak in the Chiwaukum Mountains, a subset of the Cascade Range. Its nearest higher neighbor is Snowgrass Mountain, to the northwest, and slightly lower Big Jim Mountain is set to the north-northeast. Precipitation runoff from Big Lou drains into Icicle Creek and other tributaries of the Wenatchee River. Although modest in elevation, relief is significant since Big Lou rises 5,200 feet above Icicle Creek Valley in approximately two miles. Big Lou is named for mountaineer Lou Whittaker, the twin brother of Jim Whittaker, the first American to summit Mount Everest.