Diplomat and author of Il cortegiano (The courtier). Born at Casatico to a minor landowning family of soldiers and administrators in the service of successive rulers of nearby Mantua, Castiglione was sent to Milan to have his education 'finished' on the fringe of Lodovico Sforza's court, then renowned above all others for its chivalric tone and its protection of men of learning. Though the details of this period are scarce, it is clear that it was in Milan that he acquired the military knowledge and sense for public affairs that led to his engagement successively by the rulers of Mantua (1500-04), Urbino (1504-16) and Mantua again (1516-24), and also to his lifelong, if amateur; interest in the literature of classical antiquity. Though he occupied minor military commands, his status was that of an equerry rather than of a combat soldier, and the address he brought to the arrangement of truces and liaison with allies led to his being employed increasingly as a diplomat. It was while he was residing as Mantuan ambassador in Rome that Pope Clement VII obtained leave from Duke Federico II Gonzaga to send him in 1524 as papal nuncio to Spain. Here, in Toledo; he died in 1529, mourned by Charles V as 'one of the world's finest gentlemen'.

His Latin and Italian poems appeared in print but he is remembered for his dialogue-treatise Il cortegiano (redrafted from 1508 in ever more extensive and thoughtful forms until its publication in Venice in 1528.) In it he had two aims: to give 'a portrait' of the court of Urbino at a moment (1506) he came to regard with deepening nostalgia, and to describe the formation of a courtier so widely and gracefully accomplished that his advice could, by being acceptable to a prince, contribute to the security and welfare of a badly governed Italy. Writing in an eclectic and widely accessible Italian, Castiglione employed change of pace and touches of characterization and description to bring to life people and place and to exemplify his moral imperative: never be tedious. This principle underlies his teaching that none of the courtier's attainments in arms, letters, art, sport, music or conversation should lack 'sprezzatura'; an unforced ease of accomplishment, the flavour of effortless superiority which was to be looked on for centuries as the trade mark of the gentleman. Not untainted by self-grooming for effect or snobbish scorn for overt professionalism, the notion of 'sprezzatura' nevertheless arose directly from the strain in Aristotle's and Cicero's moral philosophy which dealt with the social behaviour of the balanced and responsible citizen. Here, as in its treatment of the Platonic notion that human love can be transmuted into an apprehension of the divine, The courtier provided a skilful popularization of the ideas of humanist philosophers. Both form and content led to the book's lasting influence, first through translation (English, French, Spanish, Latin) and plagiarism, and then through absorption into the enormous literature of etiquette which it did much to stimulate.