A decommissioned highway is a highway that has been removed from service, has been shut down, or has had its authorization as a national, provincial or state highway removed. Decommissioning can include the complete or partial demolition or abandonment of an old highway structure because the old roadway has lost its utility, but such is not always the norm. Where the old highway has continuing value, it likely remains as a local road offering access to properties denied access to the new road or for use by slow vehicles such as farm equipment and horse-drawn vehicles denied use of the newer highway.

Decommissioning can also include the removal of one or more of the multiple designations of a single segment of highway. As an example, what remains as U.S. Route 60 (US 60) between Wickenburg, Arizona and Phoenix, Arizona carried the routes of three US highways (US 60, US 70, US 89) and one state highway (Arizona State Route 93). The highway remains a federal highway, but with fewer designations.