| Frederick Christian I | |
| Succession: | Duke of Schleswig-Holstein-Sonderburg-Augustenburg |
| Reign: | 20 January 1754 – 13 November 1794 |
| Predecessor: | Christian August |
| Successor: | Frederick Christian II |
| Spouse: | Princess Charlotte Amalie Wilhelmine of Schleswig-Holstein-Sonderburg-Plön |
| Issue: | Frederick Christian II Charles August, Crown Prince of Sweden |
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| Issue-Pipe: | among others... |
| House: | Oldenburg |
| Father: | Christian August, Duke of Schleswig-Holstein-Sonderburg-Augustenburg |
| Mother: | Countess Louise Frederikke af Danneskiold-Samsøe |
| Birth Place: | Augustenborg |
| Death Place: | Augustenborg |
| Religion: | Lutheranism |
Frederick Christian I (German: Friedrich Christian I., Danish: Frederik Christian 1.; 6 April 1721 – 13 November 1794) was Duke of Schleswig-Holstein-Sonderburg-Augustenburg from 1754 to 1794.
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. 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. He was a Knight of the Order of the Elephant.
On 26 May 1762, Frederick Christian married Princess Charlotte Amalie Wilhelmine (1744–1770), a daughter of Frederick Charles, Duke of Schleswig-Holstein-Sonderburg-Plön. The couple had seven children: