Frederick II (German: Friedrich; 24 January 1712 – 17 August 1786) was the third Hohenzollern king, reigning over the Kingdom of Prussia from 1740 until 1786. Frederick's achievements during his reign included his military victories, his reorganization of Prussian armies, his patronage of the Arts and the Enlightenment in Prussia, and his final success against great odds in the Seven Years' War. He became known as Frederick the Great (Friedrich der Große) and was nicknamed Der Alte Fritz ("Old Fritz") by the Prussian people.

In his youth, Frederick was more interested in music and philosophy than the art of war. He defied his authoritarian father, Frederick William I, and sought to run away with his best friend Hans Hermann von Katte. They were caught at the border and King Frederick William I nearly executed his son for desertion. After being pardoned, he was forced to watch the official beheading of Hans. Upon ascending to the Prussian throne, he attacked Austria and claimed Silesia during the Silesian Wars, winning military acclaim for himself and Prussia. Near the end of his life, Frederick physically connected most of his realm by conquering Polish territories in the First Partition of Poland. He was an influential military theorist whose analysis emerged from his extensive personal battlefield experience and covered issues of strategy, tactics, mobility and logistics.

Frederick was a proponent of enlightened absolutism. He modernized the Prussian bureaucracy and civil service and pursued religious policies throughout his realm that ranged from tolerance to segregation. He reformed the judicial system and made it possible for men not of noble stock to become judges and senior bureaucrats; he also encouraged immigrants of various nationalities to come to Prussia. Some critics, however, point out his oppressive measures against conquered Polish subjects. Frederick supported arts and philosophers he favored, but at the same time enacted several laws censoring the press. Frederick is buried at his favorite residence, Sanssouci in Potsdam. Because he died childless, Frederick was succeeded by his nephew, Frederick William II, son of his brother, Augustus William.

Nearly all 19th century German historians made Frederick into a romantic model of a glorified warrior, praising his leadership, administrative efficiency, devotion to duty and success in building up Prussia to a leading role in Europe. Historian Leopold von Ranke was unstinting in his praise of Frederick's "Heroic life, inspired by great ideas, filled with feats of arms...immortalized by the raising of the Prussian state to the rank of a power." Johann Gustav Droysen was even more extolling

Frederick, the son of Frederick William I and his wife, Sophia Dorothea of Hanover, was born in Berlin on 24 January 1712. Frederick William I, popularly dubbed as the soldier-king, had developed a strong army led by his famous Potsdam Grenadier Guards and encouraged centralized government, but he possessed a violent temper and ruled Brandenburg-Prussia with absolute authority. In contrast, Frederick’s mother Sophia was polite, charismatic and learned. Her father, George Louis of Brunswick-Lüneburg, succeeded to the British throne as King George I in 1714.