Monkeywrenching is economic warfare by sabotage, often by illegal means, used to slow down or halt an undesired government-sanctioned activity. In the United States the term is most often used in the context of ecodefense. Monkeywrenching is therefore the destruction of earth-moving equipment such as bulldozers, skip loaders, knuckle loaders, logging equipment, and road building equipment. It also includes the removal of road survey markers, billboards, certain bridges, certain power lines, certain power poles and towers, and certain roads.

The object of this destruction is generally limited to equipment that supports destructive logging, mining, and hunting activities. This means that targets are well-chosen: it is not random vandalism. Many monkeywrenchers feel they are highly ethical, and that their destructive activities are not merely justified, but laudable and necessary.

Monkeywrenching is usually an unorganized activity. Many monkeywrenchers do not know any other monkeywrencher, and perform monkeywrenching alone.

The term "Monkey-wrenching" comes from Edward Abbey's novel The Monkey Wrench Gang.