| William Frederick of Nassau-Dietz | |
|---|---|
 William Frederick of Nassau-Dietz by Wybrand de Geest, 1632 | |
| Prince of Nassau-Dietz | |
| Reign | 13 July 1640 – 31 October 1664 |
| Predecessor | Henry Casimir I |
| Successor | Henry Casimir II |
| Stadtholder of Friesland | |
| Period | 1640-1664 |
| Predecessor | Henry Casimir I |
| Successor | Henry Casimir II |
| Stadtholder of Groningen and Drenthe | |
| Period | 1650-1664 |
| Predecessor | William II |
| Successor | Henry Casimir II |
| Born | 7 August 1613 Arnhem |
| Died | 31 October 1664 (aged 51) Leeuwarden |
| Burial | Grote of Jacobijnerkerk in Leeuwarden |
| Spouse | |
| Issue |
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| House | Nassau |
| Father | Ernest Casimir I, Count of Nassau-Dietz |
| Mother | Sophia Hedwig of Brunswick-Lüneburg |
William Frederick (Dutch: Willem Frederik; Arnhem 7 August 1613 – Leeuwarden 31 October 1664), was Count (from 1654 Imperial Prince) of Nassau-Dietz, Stadtholder of Friesland, Groningen and Drenthe.