An intermodal container, often called a shipping container, is a large standardized shipping container, designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – from ship to rail to truck – 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. These containers are known under a number of names, such as simply container, cargo or freight container, ISO container, shipping, sea or ocean container, sea van or (Conex) box, container van, sea can or c can.
Intermodal containers exist in many types and a number of standardized sizes, but ninety percent of the global container fleet are so-called "dry freight" or "general purpose" containers – durable closed rectangular boxes, made of rust-retardant Corten steel; almost all 8 feet (2.44 m) wide, and of either 20 or 40 feet (6.10 or 12.19 m) standard length, as defined by ISO standard 668:2020. The worldwide standard heights are 8 feet 6 inches (2.59 m) and 9 feet 6 inches (2.90 m) – the latter are known as High Cube or Hi-Cube (HC / HQ) containers.
First invented in the early 20th century, modern 40-foot intermodal containers proliferated during the 1960s and 1970s under the containerization innovations of the American shipping company SeaLand. Just like cardboard boxes and pallets, these containers are a means to bundle cargo and goods into larger, unitized loads, that can be easily handled, moved, and stacked, and that will pack tightly in a ship or yard. Intermodal containers share a number of key construction features to withstand the stresses of intermodal shipping, to facilitate their handling and to allow stacking, as well as being identifiable through their individual, unique ISO 6346 reporting mark.
In 2012, there were about 20.5 million intermodal containers in the world of varying types to suit different cargoes. Containers have largely supplanted the traditional break bulk cargo – in 2010 containers accounted for 60% of the world's seaborne trade. The predominant alternative methods of transport carry bulk cargo – whether gaseous, liquid or solid – e.g. by bulk carrier or tank ship, tank car or truck. For air freight, the lighter weight IATA-defined unit load devices are used.