Guillermo Ducker

Guillermo Ducker (fl. 1795–1830) was a Dutch miniaturist known to have been active mainly in Madrid, Spain between 1795 and 1830. He is known to have painted for Spain's royal family as well as for Madrid's high society, until at least 1813, when he painted a miniature of Joaquina Téllez Girón, Marchioness of Santa Cruz.

Although his first known work is from 1795, the first actual mention of Ducker appears in a 1799 letter from Francisco de Goya to Spain's Secretary of State (prime minister), Mariano Luis de Urquijo in which he expressly recommends Ducker and requests Ducker's release from prison in order to paint some miniatures of Carlos IV and his family.