Cosimo also was a long-term supporter of Pope Pius V, who in the light of Florence's expansion in August 1569 declared Cosimo Grand Duke of Tuscany, a title unprecedented in Italy.
Cosimo oli ka pikaaegne paavst Pius V toetaja, kes Firenze laienemise valguses kuulutas augustis 1569 Cosimo Toscana suurhertsogiks, seda tiitlit varem Itaalias ei tuntud.