A friction stir nut is disclosed. The friction stir nut includes a body, a cap, and an anti-rotation feature. The body has an elongated cylindrical shank extending between a first end and a second end, the cap being disposed at the second end, and the anti-rotation feature being disposed at the cap and/or an outer surface of the body. The body and cap have a blind axial hole extending from the first end to the second end, the first end being blind and the second end being open. The outer surface of the first end has a flat surface oriented substantially perpendicular to the axis of the shank, and the body has a cylindrical wall thickness suitable for receiving internal threads. In response to a mandrel tool friction stir welding the friction stir nut to a workpiece and then being extracted, uniform internal threads result at the body. The anti-rotation feature bonds to the workpiece by metallurgical bonding and/or mechanical bonding.