John de Critz or John Decritz was one of a number of painters of Flemish origin active at the English royal court during the reigns of James I of England and Charles I of England. He held the post of Serjeant Painter to the king from 1603, at first jointly with Leonard Fryer and from 1610 jointly with Robert Peake the Elder.

The Serjeant Painter was an honourable and lucrative position as court painter with the English monarch. It carried with it the prerogative of painting and gilding all of the King's residences, coaches, banners, etc. and it grossed over £1,000 in a good year by the 18th century. The work itself involved painting the palaces, coaches, royal barges, and all sorts of decorations for festivities, which often had to be designed as well. The actual involvement of the serjeant painters in this gradually declined. The post itself fell out of use in the 18th century, after a period when "fine art" painters were appointed, and expected to supervise rather than execute decorative painting, for a good salary.