Picketing is a form of non-violent resistance in which people congregate outside a place of work or location where an event is taking place and attempt to dissuade others from going in ("crossing the picket line "). It has two main aims: to harm the business or activity by losing it custom or workers, and to propogandise for the issue at stake.

Picketing is a common tactic used by trade unions during strikes, who will try to prevent dissident members of the union, members of other unions and ununionised workers from working. Those who cross the picket line and work despite the strike are known as scabs.

A mass picket is an attempt to bring as many people as possible to a picket line, in order to demonstrate support for the cause. It is a particularly useful tactic when only one workplace is being picketed, or for a symbolically or practically important workplace. Due to the numbers involved, a mass picket may turn in to a blockade.

Picketing is also used by pressure groups across the political spectrum.

While picketing is often legal in certain countries due to freedom of assembly laws, most countries have severe restrictions on its use.