Railroad classes are the system by which freight railroads are designated in the United States. Railroads are assigned to Class I, II or III according to annual revenue criteria originally set by the Surface Transportation Board in 1992. With annual adjustments for inflation, the 2019 thresholds were US$504,803,294 for Class I carriers and US$40,384,263 for Class II carriers.

The Surface Transportation Board (STB) of the United States is an independent federal agency that serves as an adjudicatory board. The board was created in 1996 following the abolition of the Interstate Commerce Commission (ICC) and absorbed regulatory powers relevant to the railroad industry previously under the ICC's purview.