Charles William Ferdinand, Duke of Brunswick-Lüneburg, Prince of Brunswick-Wolfenbüttel (German: Karl Wilhelm Ferdinand, Herzog von Braunschweig-Lüneburg und Fürst von Braunschweig-Wolfenbüttel) (9 October 1735 – 10 November 1806), was ruler of Brunswick-Wolfenbüttel, a statesman and a military leader. His titles are usually shortened to Duke of Brunswick in English-language sources.

He succeeded his father as sovereign prince of the Principality of Brunswick-Wolfenbüttel, one of the princely states of the Holy Roman Empire. He was a recognized master of the warfare of the mid-18th century who served as a Generalfeldmarschall of the Kingdom of Prussia. The duke was a cultured and benevolent despot in the model of Frederick the Great, and was married to Princess Augusta, a sister of George III of Great Britain.

Charles William Ferdinand was born in the town of Wolfenbüttel on 9 October 1735, probably in the Schloss Wolfenbüttel () palace. He was the first-born son of Charles I, Duke of Brunswick-Wolfenbüttel and his wife Philippine Charlotte.

Charles I was the ruling prince (German: Fürst) of the small state of Brunswick-Wolfenbüttel, one of the imperial states of the Holy Roman Empire. Philippine Charlotte was the favourite daughter of King Frederick William I of Prussia and sister of Frederick II of Prussia (Frederick the Great). As the heir apparent of a sovereign prince, Charles William Ferdinand received the title of Hereditary Prince (German: Erbprinz).