| Ernest Günther | |
| Succession: | Duke of Schleswig-Holstein-Sonderburg-Augustenburg |
| Reign: | 13 May 1627 - 18 January 1689 |
| Successor: | Frederick |
| Spouse: | Augusta of Schleswig-Holstein-Sonderburg-Glücksburg |
| Issue: | Frederick Princess Sophie Amalie Prince Philipp Ernst Princess Sophie Auguste Louise Charlotte, Duchess of Beck Princess Ernestine Justine Ernest August Dorothea Louise, Princess-Abbess of Itzehoe Prince Frederick William |
| House: | House of Schleswig-Holstein-Sonderburg-Augustenburg |
| Father: | Alexander, Duke of Schleswig-Holstein-Sonderburg |
| Mother: | Dorothea of Schwarzburg-Sondershausen |
| Birth Date: | 14 October 1609 |
| Birth Place: | Sønderborg, Denmark |
| Death Place: | Augustenborg Palace, Augustenborg, Denmark |
Ernest Günther I of Schleswig-Holstein-Sonderburg-Augustenburg (14 October 1609 - 18 January 1689) was a Duke of Schleswig-Holstein of its Sonderburg line.[1] He was the first to have his ducal seat in Augustenborg Palace, which he built and named in honor of his wife.[2] He ruled from 1647 until his death in 1689.[3]
He was third son of Alexander, Duke of Schleswig-Holstein-Sonderburg and his wife, Countess Dorothea of Schwarzburg-Sondershausen (1579-1639).
On 15 June 1651 he married Princess Auguste of Schleswig-Holstein-Sonderburg-Glücksburg (27 June 1633 - 26 May 1701), daughter of Duke Philipp of Schleswig-Holstein-Sonderburg-Glücksburg and his wife, Princess Sophie Hedwig of Saxe-Lauenburg (1601-1660).[4] They had ten children: