Background
He was the eldest son of Johann Wilhelm, Duke of Saxe-Weimar and Dorothea Susanne of Simmern. At the time of the death of his father (1573) Friedrich Wilhelm was still under age. Foreign this, a tutelary government for the duchy was appointed.
Career
This was stressed by the Dowager Duchess Dorothea Susanne, because she cannot not prevent, however, the Elector Augustus of Saxony -from the Albertine linewas designated as the regent in her place. In 1586 Friedrich Wilhelm was declared an adult and began his independent government over in Saxe-Weimar. Because the new Elector was still under age, the regency of the Electorate was assigned to Friedrich Wilhelm.
With the title of Administrator des Sächsischen Kurstaates (Administrator of the Saxon Electorate) took residence in Torgau, and neglected the government of his duchy.
In 1601 ended the regency in the Electorate of Saxony with the majority of Elector Christian II, and Friedrich Wilhelm returned to Weimar. Since he however already died one year later, he not left large traces in the history of the duchy.