Son of Frederick Christian (1722-1763), Elector of Saxony, and Maria Antonia Walpurgis of Bavaria (1724-1780).
He became Elector of Saxony, as Friedrich August III, following the death of his father in 1763, but his mother Maria Antonia, and uncle Franz Xavier, ruled on his behalf until his coming-of-age in 1768. Following the dissolution of the Holy Roman Empire, he became King Friedrich August I of Saxony in December 1806.
In 1769 he married Maria Amalia Augusta of Zweibrücken-Birkenfeld, a Countess Palatine. The couple had only one surviving child, the Princess Maria Augusta (1782-1863). As a consequence, Frederick Augustus was succeeded as King of Saxony by his brother Anton (1755-1836).
Boswell visited the Court of Saxony in Dresden on October 12, 1764, and subsequently described Friedrich August as “a sweet prince”.