Frederick Christian I was Duke of Schleswig-Holstein-Sonderburg-Augustenburg.
Background
He was the eldest son of Christian August, Duke of Schleswig-Holstein-Sonderburg-Augustenburg (1696–1754) and his wife Duchess Louise Frederikke née Countess af Danneskiold-Samsøe (1699–1744). In 1754, his father died and Frederick Christian inherited Augustenborg Castle and Gråsten.
Career
However, these estates were deeply in debt. He waived his claims on the duchies of Schleswig and Holstein and in return the King of Denmark (who was also Duke of Schleswig and Holstein) granted him a favourable settlement. This allowed him to purchase Als and Sundeved, making him the largest landowner in Schleswig.
He was also able to expand Augustenborg Castle, the family residence.
Frederick Christian served as a general in the Danish army.