Strike action, often simply called a strike, is a work stoppage caused by the mass refusal by employees to perform work. A strike usually takes place in response to employee grievances. Strikes became important during the industrial revolution, when mass labour became important in factories and mines. In most countries, they were quickly made illegal, as factory owners had far more political power than workers. Most western countries partially legalized striking in the late 19th or early 20th centuries.

Strikes are sometimes used to put pressure on governments to change policies. Occasionally, strikes destabilise the rule of a particular political party. A notable example is the Gdańsk Shipyard strike led by Lech Wałęsa. This strike was significant in the struggle for political change in Poland, and was an important mobilised effort that contributed to the fall of governments in communist East Europe.