Guillaume Cale (sometimes anglicized to William Kale, also known as Guillaume Caillet, popularly known as Jacques Bonhomme ("Jack Goodfellow") or Callet) was a peasant from the village of Mello near Beauvais, who became leader of the peasant Jacquerie which broke out in May 1358 and continued for a month unchecked until the Battle of Mello on 10 June. Cale's origins are unknown; it is not clear how old he was at the time of the uprising, nor is anything known about his family and business ties, except that he was a reasonably well-off farmer.
In 1358 the Beauvais was perhaps the only region of France that had remained unaffected by twenty years of warfare with England. It was still prosperous despite the impact of the Black Death, and maintained its wealth under the protection of the household troops of the French king and the other nobles who lived in and around Paris, depending on the region for food and for taxation income. However, in 1356, King John II was captured by the English at the Battle of Poitiers. His exorbitant ransom began to drain the already depleted French treasury, and the authority exercised by the nobility diminished. In the spring of 1358, violence broke out in Paris, as a clothier named Étienne Marcel seized the city with an army of townsmen, drove out the Dauphin and formed a revolutionary commune, presided over by Marcel.