| Frederick III | |
| Succession: | Duke of Holstein-Gottorp |
| Reign: | 31 March 1616 – 10 August 1659 |
| Predecessor: | John Adolf |
| Successor: | Christian Albert |
| House: | Holstein-Gottorp |
| Father: | John Adolf, Duke of Holstein-Gottorp |
| Mother: | Augusta of Denmark |
| Spouse: | Duchess Marie Elisabeth of Saxony |
| Issue: | Sofie Auguste, Princess of Anhalt-Zerbst Magdalene Sibylle, Duchess of Mecklenburg-Güstrow Johann Adolf Marie Elisabeth, Landgravine of Hesse-Darmstadt Friedrich Hedwig Eleonora, Queen of Sweden Adolf August Johann Georg Anna Dorothea Christian Albert, Duke of Holstein-Gottorp Gustav Ulrich Christine Sabine August Friedrich, Prince-Regent of Eutin and Prince-Bishop of Lübeck Adolf Elisabeth Sofie Auguste Marie, Margravine of Baden-Durlach |
| Birth Date: | 22 December 1597 |
| Birth Place: | Gottorf Castle |
| Death Place: | Tönning |
| Burial Place: | Schleswig Cathedral |
Frederick III of Holstein-Gottorp (22 December 1597 - 10 August 1659) was a Duke of Holstein-Gottorp.
He was the elder son of Duke Johann Adolf of Holstein-Gottorp and Princess Augusta of Denmark. His mother was a daughter of King Frederick II of Denmark.He had ambitious plans concerning the development of sea trade. With this purpose he established Friedrichstadt in 1621, in sympathy with city of Glückstadt established in 1617 by Christian IV of Denmark. Furthermore, he attempted to find a commercial way to Russia and Persia that would not pass around Africa. For this reason he sent on 6 November 1633 the expedition from Hamburg to Moscow under the management of a commercial agent of Otto Brüggemann and a ducal adviser, Philipp Crusius, and with Adam Olearius as secretary. On 14 August 1634 the delegation arrived at Moscow. Although it was not successful in concluding a commercial agreement with Tsar Michael I of Russia, nevertheless, immediately after the return of the delegation to Gottorp on 6 April 1635, Frederick began the preparation of the following expedition. In 1636, he sent his delegation to Persia, and in 1639 Safi of Persia sent a return delegation with presents for the Duke.
The difficult task of leading the country through the Thirty Years' War confronted Frederick. He tried a policy of neutrality, which meant in practice the refusal of the union with Denmark and inclinations toward Sweden. In 1654 he hosted the recently abdicated Christina, Queen of Sweden. She wrote to her successor to recommend two of his daughters as potential brides. Thus, he married his daughter Hedvig Eleonora to King Charles X of Sweden. Since the Swedish attempt at being the Great Power ultimately failed, Frederick's pro-Swedish policy led to the weakening of the house of Holstein-Gottorp.
Frederick as the patron of art and culture was more successful. Thus he founded on 3 September 1642 together with Prince Louis I of Anhalt-Köthen the Fruitbearing Society. Furthermore, he contributed to the creation of the Globe of Gottorf. The painter Jürgen Ovens worked more than 30 years for him and his successor Christian Albrecht of Holstein-Gottorp.
Frederick died in 1659 in the fortress of Tönning, while the fortress was besieged in the course of the Second Karl Gustav War between Denmark and Sweden.
He was married in Dresden on 21 February 1630 to Princess Marie Elisabeth of Saxony, daughter of Elector John George I of Saxony and Magdalene Sibylle of Prussia. They had sixteen children, ten of whom lived to adulthood: