the grand duchy of tuscany (, ) was a monarchy in tuscany, an area in the north-west of the italian peninsula. it existed, with interruptions, from 1569 to 1859. it replaced the duchy of florence. it was ruled by the grand duke of tuscany. the capital of the grand duchy was florence. until the house of lorraine took over from the medici, tuscany was a state of the holy roman empire until the peace of westphalia in 1648. under the medici the heir to the grand ducal throne was called the "grand prince of tuscany" whereas the lorrainers used various titles for the heir apparent.