Chatham Dockyard was a Royal Navy Dockyard located on the River Medway in Kent. It was established in Chatham in the mid-16th century. The dockyard was then expanded into neighbouring Gillingham. Chatham Dockyards and its Defences are UNESCO World Heritage Sites.
It existed after the Reformation. It was at a time when relations with the Catholic countries of Europe had worsened, which increased the need for additional defences.