RORO is an acronym for "Roll On/Roll Off"; a type of ferry ship that carries wheeled cargo such as vehicles, trailers or railway carriages.

ROROs have their own built-in ramps on board, which allow the cargo to be "rolled on" and "rolled off" the vessel when the ramp is in a down or 'open' position.

Car Ferries that operate across rivers and other short distances which are generally not referred to as ROROs, as this acronym is reserved for ships.

Typically new automobiles that are imported/exported by ship around the world are moved on ROROs. These large new-car carriers are commonly called "PCC's" or "PCTC's": Pure Car Carriers or Pure Car Truck Carriers respectively.

The largest PCC, which is expected to be launched in 2006 will be able to carry 8,000 automobiles.

The sea going RORO car ferry, with big external doors close to the waterline and a large open vehicle deck, has a reputation for being a high risk design. If any water enters the vehicle deck, it quickly accumulates on one side of the deck making the ship unstable and causing a capsize as happened with the Princess Victoria in 1953 killing 132 people, the M/S Herald of Free Enterprise in 1987 killing 193 people, and the M/S Estonia in 1994 killing 852 people.