A ship fitted with a drilling derrick that is used to drill in waters that are too deep for jack-up rigs and semi-submersible rigs.

A vessel modified to include a drilling rig and special station-keeping equipment.

A drillship is a maritime vessel that has been fitted with drilling apparatus. It is most often used for exploratory drilling of new oil or gas wells in deep water but can also be used for scientific drilling. It is often built on a modified tanker hull and outfitted with a dynamic positioning system to maintain its position over the well.