He belonged to the Albertine branch of the House of Wettin and was the eldest son of John George III, Elector of Saxony and Anna Sophie of Denmark.

At the beginning of his reign his chief adviser was Hans Adam von Schöning, who counselled a union between Saxony and Brandenburg and a more independent attitude towards the emperor.

In accordance with this advice certain proposals were put before Leopold I to which he refused to agree; and consequently the Saxon troops withdrew from the imperial army, a proceeding which led the chagrined emperor to seize and imprison Schöning in July 1692.

Although John George was unable to procure his minister's release, Leopold managed to allay the elector's anger, and early in 1693 the Saxon soldiers rejoined the imperialists.

When John George tried to stab Eleonore with a sword, the unarmed Frederick stopped the weapon with his hand, injuring it and leaving him with a lifelong handicap.