Jan van Hembyse or Hembyze (Ghent, 9 July 1513 – Ghent, 8 August 1584) was a Flemish politician and popular leader, with a demagogic tendency, who together with François van Ryhove brought about the Calvinist Republic of Ghent and for two periods (1577-1578 and 1583-1584) led that regime in the early stage of the Dutch Revolt and the Eighty Years' War as it unfolded in the County of Flanders.