Portrait of Cosimo I de' Medici

Giorgio Vasari's Portrait of Cosimo I de' Medici, executed in fresco in 1558 in the Palazzo Vecchio, is among the most formally significant of the many likenesses he produced of his principal patron and employer. Cosimo I had ruled Florence since 1537 and by 1558 had transformed the city from a nominal republic into a centralised duchy; he would be recognised as Grand Duke of Tuscany in 1569. A fresco portrait within the Palazzo Vecchio — the seat of Florentine government — served a specifically political function distinct from the easel portraits that circulated among collectors: it inscribed Cosimo's image permanently into the walls of his own palace, making his physical presence an architectural fact rather than a moveable object. Vasari's portrait would have drawn on Cosimo's established iconography while adding the authority and permanence that fresco conveyed.

Fresco portrait technique required Vasari to capture Cosimo's recognised likeness with the decisive, unflinching application that wet plaster demanded. The duke's armour or formal dress would be rendered with the broad, confident strokes that fresco favours, while the face received the most careful attention — the feature most scrutinised by viewers who knew the duke personally.