John VI, Prince of Anhalt-Zerbst

John VI of Anhalt-Zerbst (Zerbst, 24 March 1621 – Zerbst, 4 July 1667), was a German prince of the House of Ascania and ruler of the principality of Anhalt-Zerbst.
He was the only son of Rudolph, Prince of Anhalt-Zerbst, by his second wife Magdalene, daughter of John VII, Count of Oldenburg.
John VI is also an ancestor of Prince William, Duke of Cambridge and Prince Harry, for his great-great-grandson Paul I of Russia is a great-great-grandfather of Prince Andrew of Greece and Denmark, great-grandfather of the Princes through his only son Prince Philip, Duke of Edinburgh. He is also their ancestor through Princess Augusta of Saxe-Gotha, Princess of Wales.

John succeeded his father in Anhalt-Zerbst at only four months of age; during his long minority, his paternal uncle Augustus of Anhalt-Plötzkau acted as regent in the principality.

John's education was supervised primarily by his mother. Political instability caused by warfare during the Thirty Years War caused John to be educated in Zerbst, Coswig, and Wittenberg at various times. From 1633 he continued his education at the court of his maternal uncle Anthony Günther, Count of Oldenburg.

Immediately after he reached adulthood and formally assumed the government of his state, John made Lutheranism the official religion of Zerbst. He increased the size of his principality noticeably by acquiring various fiefs.

In 1642 his uncle Louis of Anhalt-Köthen, admitted John to the Fruitbearing Society together with the Hofrat Konrad Balthasar Pichtel and the Hofjunker Joachim von Boeselager. He chose the motto anmutiger Schärfe ("graceful sharpness"). As an emblem the flower Tropaeolaceae was reserved for him.

In Gottorp on 16 September 1649 John married Sophie Auguste (b. Gottorp, 5 December 1630 – d. Coswig, 12 December 1680), daughter of Frederick III, Duke of Schleswig-Holstein-Gottorp. They had fourteen children:

1. John Frederick, Hereditary Prince of Anhalt-Zerbst (b. Zerbst, 11 October 1650 – d. Zerbst, 13 March 1651).
2. George Rudolph, Hereditary Prince of Anhalt-Zerbst (b. Zerbst, 8 September 1651 – d. Zerbst, 26 February 1652).
3. Karl William, Prince of Anhalt-Zerbst (b. Zerbst, 16 October 1652 – d. Zerbst, 8 November 1718).
4. Anthony Günther, Prince of Anhalt-Mühlingen (b. Zerbst, 11 January 1653 – d. Zerbst, 10 December 1714).
5. John Adolph (b. Zerbst, 2 December 1654 – d. Zerbst, 19 March 1726).
6. John Louis I, Prince of Anhalt-Zerbst-Dornburg (b. Zerbst, 4 May 1656 – d. Dornburg, 1 November 1704).
7. Joachim Ernest (b. Zerbst, 30 July 1657 – d. Zerbst, 4 June 1658).
8. Magdalene Sophie (b. Zerbst, 31 October 1658 – d. Zerbst, 30 March 1659).
9. Frederick (b. Zerbst, 11 July 1660 – d. Zerbst, 24 November 1660).
10. Hedwig Marie Eleonore (b. Zerbst, 30 January 1662 – d. Zerbst, 30 June 1662).
11. Sophie Auguste (b. Zerbst, 9 March 1663 – d. Weimar, 14 September 1694), married on 11 October 1685 to Johann Ernst III, Duke of Saxe-Weimar.
12. A daughter (b. and d. Zerbst, 12 February 1664).
13. Albert (b. and d. Zerbst, 12 February 1665).
14. Augustus (b. Zerbst, 23 August 1666 – d. Zerbst, 7 April 1667).