independent federal agency created by the U.S. Congress in 1935 to administer the National Labor Relations Act (also called the Wagner Act). The act was amended in 1947 through the Taft-Hartley Act (Taft–Hartley Act) and in 1959 through the Landrum-Griffin (Landrum-Griffin Act) Act.

The primary functions of the NLRB are (1) to decide, when petitioned by employees, if an appropriate bargaining unit of employees exists for collective bargaining; (2) to determine by secret-ballot elections (conducted by the NLRB) whether the employees in a business or industry wish to be represented by labour unions; and (3) to prevent or correct unfair labour practices by employers and unions.

Appointed by the U.S. president, the five board members and the general counsel serve different purposes. The board is charged with hearing labour disputes and resolving them through quasi-judicial proceedings. The NLRB's general counsel investigates and prosecutes complaints and also oversees cases in the NLRB's field offices.

The NLRB has no independent power to enforce its orders but may seek enforcement through a U.S. court of appeals. The board may not act on its own motion; in all cases charges and representation petitions must be initiated by employers, individuals, or unions. Over time, the decisions made by the NLRB have done much to shape American labour practices.