McMillan Spire () is a mountain peak in the Picket Range in the U.S. state of Washington and within North Cascades National Park. The peak lies east of Mount Degenhardt, and east of Inspiration Peak. The subpeak known as East McMillan Spire () is east of McMillan Spire and they are collectively referred to as the McMillan Spires. The Terror Glacier lies to the west of the peak.