Big Jim Mountain is a mountain summit located in Chelan County of Washington state. It is situated northwest of Leavenworth, within the Alpine Lakes Wilderness, on land managed by Okanogan-Wenatchee National Forest. Big Jim Mountain is the fourth-highest peak in the Chiwaukum Mountains, a subset of the Cascade Range. Its nearest higher neighbor is Big Lou, to the south-southwest, and Cape Horn is set to the west. Precipitation runoff from Big Jim drains into tributaries of the Wenatchee River. Although modest in elevation, relief is significant since Big Jim rises 2,300 feet above Painter Creek Valley in one mile. Big Jim Mountain is named for Jim Whittaker, the first American to summit Mount Everest and twin brother of Lou Whittaker.