An acting governor is a constitutional position created in some U.S. states when the governor dies in office or resigns. In some states, the governor may also be declared to be incapacitated and unable to function for various reasons, including illness and absence from the state for more than a specified period.

In these instances, the state constitution will declare which official is to serve as governor, and whether this person will have all of the powers of the office or only specified ones. In many states, the person succeeding to the governorship or becoming acting governor is the lieutenant governor; however, not all states have such a position. If the state consititution provides for an acting governor in the event of the governor's disability, it will also provide for a method by which the governor can be declared to be no longer disabled.

The powers of an acting governor came into dispute during the 1980 Democratic primary presidential campaign of Jerry Brown, then governor of California. When he was out of state campaigning, which was often in late 1979 and early 1980, Mike Curb, a Republican who was then serving as Lieutenant Governor of California often used his position as acting governor to veto legislation, promulgate executive orders, issue proclamations, and to do other things that Brown would not likely have done had he been present in the state. This eventually resulted in litigation, much of which went in Curb's favor.

See also: Acting President; Acting (law)