Mount Aix is a mountain summit centrally located in the William O. Douglas Wilderness on land administered by the Wenatchee National Forest, and is the highest point in that wilderness area. It is also 24 miles east-southeast of Mount Rainier in Yakima County of Washington state. Mount Aix is situated east of the crest of the Cascade Range, southeast of Bumping Lake, north of Bismarck Peak, and northwest of Rimrock Lake. Its nearest higher peak is Tieton Peak in the Goat Rocks Wilderness, to the south-southwest. Mount Aix is the highest peak in the entire region which is east of Mount Rainier National Park, north of Goat Rocks Wilderness, west of Yakima, and south of Mount Daniel (Alpine Lakes Wilderness), so it is quite prominent. Prior to 1897 (when Mount Aix was officially recognized by the USGS) the name was spelled as Mount Aiks on early survey maps and publications.