John May Sr or Jan Maij was an English shipwright from Chatham who served from 1758-1779 as Master Shipbuilder of the Amsterdam Admiralty.

The Admiralty of Amsterdam was the largest of the five Dutch admiralties at the time of the Dutch Republic. The administration of the various admiralties was strongly influenced by provincial interests. The territory for which Amsterdam was responsible was limited to the city itself, the Gooi region, the islands of Texel, Vlieland and Terschelling, the province of Utrecht and the Gelderland quarters of Arnhem and of the Graafschap (county) of Zutphen. Amsterdam had developed into the most important of all the admiralties and often compensated for the other admiralties' deficiencies. When the "Committee for Naval Affairs" replaced the Admiralty Colleges on 27 February 1795 during the reforms by the Batavian Republic, the lower civil servants were kept on, but the officers were dismissed.