John Parker (c.1500–1564) was an English-born merchant, politician and judge in Tudor Ireland. He held the offices of Constable of Dublin Castle and Master of the Rolls in Ireland; to be appointed to the latter office was a notable achievement for a man who began his career as a cloth-maker and had no legal qualifications which would qualify him for judicial office. He also sat in the Irish House of Commons in the Parliament of 1560, and was a member of the Irish Privy Council. As a politician he was noted for leading the opposition to the Earl of Sussex, the Lord Deputy of Ireland, in the early 1560s.