An intermodal container, often called a shipping container, or a freight container, (or simply “container”) is a large standardized container designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – such as from ships to trains to trucks – without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well. It is like a boxcar that does not have wheels. Based on size alone, up to 95% of intermodal containers comply with ISO standards, and can officially be called ISO containers. These containers are known by many names: cargo container, sea container, ocean container, container van or sea van, sea can or C can, or MILVAN, or SEAVAN. The term CONEX (Box) is a technically incorrect carry-over usage of the name of an important predecessor of the ISO containers: the much smaller steel CONEX boxes used by the U.S. Army.

Intermodal freight transport involves the transportation of freight in an intermodal container or vehicle, using multiple modes of transportation, without any handling of the freight itself when changing modes. The method reduces cargo handling, and so improves security, reduces damage and loss, and allows freight to be transported faster. Reduced costs over road trucking is the key benefit for inter-continental use. This may be offset by reduced timings for road transport over shorter distances.