Tahtlum Peak is a 6,567-foot-elevation (2,002 meter) mountain summit in Yakima County of Washington state.

Tahtlum Peak is located east-southeast of Chinook Pass and north of Dewey Lake in the William O. Douglas Wilderness.

It is part of the Cascade Range and the nearest higher neighbor is Dewey Peak, 1.61 mi (2.59 km) to the south.

Most weather fronts originate in the Pacific Ocean, and travel east toward the Cascade Mountains.

As a result, the west side of the North Cascades experiences high precipitation, especially during the winter months in the form of snowfall.