A labor lockout is an effort by bosses to block workers from working in the midst of a labor dispute. When unionizing, employers will often use a variety of these union-busting tactics in an attempt to dissuade, dissolve, and dishearten their workers and their unions. Employers will draw out negotiations in an effort to undermine or halt union efforts, partner with anti-union firms, and even refuse to allow employees to work.

Lockouts are often accomplished by literally locking employees out of the workplace, but they can also be achieved through work stoppages, layoffs, or the hiring of nonunion replacement workers. This generally results in a pause in workplace activity, in the case of the employer closing down, and the suspension of employee contracts until an agreement is reached in bargaining.