Refitting or refit of boats and marine vessels includes repairing, fixing, restoring, renewing, mending, and renovating an old vessel. Refitting has become one of the most important activities inside a shipyard. It offers a variety of services for an old vessel of any size and kind starting with the construction itself and what is added to it, such as hardware, electric & hydraulic systems, entertainment systems, etc.^{[citation needed]}

Ship refits can range from relatively small changes to and including cutting the ship in half to facilitate near-total overhauls and redesign of interior spaces and modification or replacement of engines, systems or other equipment.

Refitting can be divided^{[according to whom?]} into several main subjects:

Examples of recent ship refits include: