Which Prussian king was a leading Enlightenment figure and corresponded with Voltaire?

The Prussian king who became a leading Enlightenment figure and corresponded with Voltaire was Frederick the Great. He ruled Prussia as Frederick II from 1740 until 1786 and cultivated an image of himself as a philosopher-king.

Frederick admired French culture and wrote many of his own works in French. He began corresponding with Voltaire in 1736, when he was still Crown Prince. Their relationship later became personal: Voltaire visited Frederick’s court and spent time at Sanssouci, the king’s palace near Potsdam.

Their friendship was complicated. Frederick valued Voltaire’s wit and intellectual reputation, while Voltaire sometimes criticized the king’s behavior and court. After a bitter dispute in the early 1750s, they separated, though their correspondence eventually resumed.

Frederick was also a practical ruler and military commander, especially during the Seven Years’ War. That combination—philosophical interests alongside strong absolutist rule—is why historians often describe him as an example of enlightened absolutism. Catherine the Great and Joseph II were also associated with Enlightenment ideas, but neither was Prussian king.