John or Jan van Diest (died 1 June 1340) was bishop of Utrecht from 1322 to 1340. Jan descended from a noble family from Brabant, and was initially provost of Cambrai. In 1322 Jan was proposed as candidate for the Bishopric of Utrecht by William III, Count of Holland and Reginald II of Guelders, much against the wishes of the Utrecht chapters, who had chosen Jan van Bronkhorst. The latter was confirmed by the archbishop of Cologne, but Pope John XXII intervened, declaring the choice of the Utrecht chapters void, and personally consecrated Jan van Diest in Avignon. It was not until 1327 that Jan was dedicated as priest.