Container ship "Rita" being loaded at Copenhagen; note crew standing on deck, and stacks of containers on shore.

Container ships are cargo ships that carry all of their load in truck-size containers, in a technique called containerization.

Informally known as "box boats," they carry the majority of the world's dry cargo . There are large main line vessels that ply the deep sea routes, then many small "feeder" ships that supply the large ships at centralized hub ports. Most container ships are propelled by diesel engines, and have crews of between 20 and 40 people. They generally have a large accommodation block at the stern, directly above the engine room.

The first container ships were converted tankers, built up from surplus tanker Liberty ships after World War II. Container ships are by now, all purpose-built and, as a class, they are the biggest cargo ships on the oceans, right after crude oil carriers, or tankers.

Container ship "CMA CGM Balzac" in the port of Zeebrugge Belgium.