Duke of Grimaldi () is a hereditary title of Spanish nobility, accompanied by the dignity of Grandee. It was created in 1777 by Charles III to Pablo Jerónimo de Grimaldi, a member of the House of Grimaldi and marquess of Grimaldi in Geneva, that served as prime minister of Spain from 1763 to 1777.
When the second duke died, the title became vacant for almost a century, until Alfonso XIII reinstated it on behalf of MarÃÂa del Rosario Patiño y Losada, the most senior direct descendant of the last titleholder, thus becoming the 3rd Duchess of Grimaldi in 1927.