A ship replica is a reconstruction of a no longer existing ship. Replicas can range from authentically reconstructed, fully seaworthy ships, to ships of modern construction that give an impression of a historic vessel. Some replicas may not even be seaworthy, but built for other educational or entertainment purposes.
Reasons to build a replica include historic research into shipbuilding, national pride, exposition at a museum or entertainment (e.g., for a TV series), and/or education programs for the unemployed. For example, see the project to build a replica of the Continental brig Andrew Doria. Apart from building a genuine replica of the ship, sometimes the construction materials, tools and methods can also copied from the ships' original era, as is the case with the replica of Batavia in Lelystad and the ship of the line replica Delft in Rotterdam (Delfshaven).
The term "replica" in this context does not normally include scale models. The term museum ship is used for an old ship that has been preserved and converted into a museum open to the public.
A ship replica may also be a generic replica, one that represents a certain type of ship rather than a particular historic example, like Kamper Kogge, replicating the Cogs that were used extensively in Northern Europe by the Hanseatic League in the Middle Ages, but where there is little knowledge of specific ships.
Some generic type replicas such as Thor Heyerdahl's Ra II, qualify as true replicas as these ships were built to investigate the craft and or culture of the original era. That they do not replicate a specific vessel is mainly because no details of such a specific vessel are available.