ISO 668 in the context of ISO container

An intermodal container, often called a shipping container, or a freight container, (or simply "container") is a large metal crate 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 containers exist in many types and standardized sizes, but 90 percent of the global container fleet are "dry freight" or "general purpose" containers: durable closed rectangular boxes, made of rust-retardant weathering steel; almost all 8 feet (2.4 m) wide, and of either 20 or 40 feet (6.1 or 12.2 m) standard length, as defined by International Organization for Standardization (ISO) standard 668:2020. The worldwide standard heights are 8 feet 6 inches (2.6 m) and 9 feet 6 inches (2.9 m) – the latter are known as High Cube or Hi-Cube (HC or HQ) containers. Depending on the source, these containers may be termed TEUs (twenty-foot equivalent units), reflecting the 20- or 40-foot dimensions.

This article lists the world's busiest container ports (ports with container terminals that specialize in handling goods transported in intermodal shipping containers), by total number of twenty-foot equivalent units (TEUs) transported through the port. The table lists volume in thousands of TEU per year. The vast majority of containers moved by large, ocean-faring container ships are 20-foot (1 TEU) and 40-foot (2 TEU) ISO-standard shipping containers, with 40-foot units outnumbering 20-foot units to such an extent that the actual number of containers moved is between 55%–60% of the number of TEUs counted.

The latest ranking reflected the figures for the year 2025, as published in the Lloyds List Top 100 and World Shipping Council (2025 figures), unless otherwise indicated.

A container ship (also called boxship or spelled containership) is a cargo ship that carries all of its load in truck-size intermodal containers, in a technique called containerization. Container ships are a common means of commercial intermodal freight transport and now carry most seagoing non-bulk cargo.

Container ship capacity is measured in twenty-foot equivalent units (TEU). Typical loads are a mix of 20-foot (1-TEU) and 40-foot (2-TEU) ISO-standard containers, with the latter predominant.

The CONEX box, a portmanteau of "Container, express", is a type of cargo container that was developed during the Korean War and was used to transport and store supplies during the Korean and Vietnam wars. It was reinvented by Malcom McLean to form the standard intermodal shipping container, often called an ISO box, after ISO 668/ISO 6346, that is used widely by container shipping companies today.