A flatcar (US) (also flat car, or flatbed) is a piece of rolling stock that consists of an open, flat deck mounted on trucks (US) or bogies (UK) at each end. Occasionally, flat cars designed to carry extra heavy or extra large loads are mounted on a pair (or rarely, more) of bogies under each end. The deck of the car can be wood or steel, and the sides of the deck can include pockets for stakes or tie-down points to secure loads. Flatcars designed for carrying machinery have sliding chain assemblies recessed in the deck.

Flatcars are used for loads that are too large or cumbersome to load in enclosed cars such as boxcars, but which will not be harmed by the weather. They are also often used to transport intermodal containers (shipping containers) or trailers as part of intermodal freight transport shipping.

Aircraft parts were hauled via conventional freight cars beginning in World War II. However, given the ever-increasing size of aircraft assemblies, the "Sky Box" method of shipping parts was developed in the late 1960s specifically to transport parts for the Boeing 747 and other "jumbo" jets of the time. The "Sky Box" consists of a two-piece metal shell that is placed atop a standard flatcar to support and protect wing and tail assemblies and fuselage sections in transit (originally, depressed-center or "fish belly" cars were utilized).

Boeing 737 aircraft fuselages constructed by Spirit Aerosystems in Wichita, Kansas are hauled as special loads to the Boeing Renton Factory for final assembly.

Bulkhead flatcars are designed with sturdy end-walls (bulkheads) to prevent loads from shifting past the ends of the car. Loads typically carried are pipe, steel slabs, utility poles and lumber, though lumber and utility poles are increasingly being hauled by skeleton cars. Bulkheads are typically lightweight when empty. An empty bulkhead on a train puts it at a speed restriction to go no more than 50 mph (80 km/h). Since bulkheads are lightweight when empty, hunting can occur when the car is above 50 mph (80 km/h). Hunting is the wobbling movement of the trucks on a freight car or a locomotive. If the wheels hunt against the rails for a period of time, there is a high risk of a derailment.

Centerbeam flatcars, centerbeams, center partition railcar, or "lumber racks" are specialty cars designed for carrying bundled building supplies such as dimensional lumber, wallboard, and fence posts. They are essentially bulkhead flatcars that have been reinforced by a longitudinal I-beam, often in the form of a Vierendeel truss, sometimes reinforced by diagonal members, but originally in the form of stressed panels perforated by panel-lightening "opera windows", either oval-shaped (seen above) or egg-shaped. These flatcars must be loaded symmetrically, with half of the payload on one side of the centerbeam and half on the other, to avoid tipping over.

Heavy capacity flatcars are cars designed to carry more than 100 short tons (90.72 t; 89.29 long tons). They often have more than the typical North American standard of four axles (one two-axle truck at each end), and may have a depressed center to handle excess-height loads as well as two trucks of three axles each (one at each end) or four trucks (two at each end) of two axles each, connected by span bolsters. Loads typically handled include electrical power equipment and large industrial production machinery.

A circus train is a modern method of conveyance for circus troupes. One of the larger users of circus trains was the Ringling Bros. and Barnum & Bailey Circus (RBBX), a famous American circus formed when the Ringling Brothers Circus purchased the Barnum and Bailey Circus in 1907, merged in 1919, and closed permanently as a merged company in May 2017.