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 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. 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. He was also a recognized master of 18th century warfare, serving as a Field Marshal in the Prussian Army. During the Napoleonic Wars, he was mortally wounded by a musket ball at the Battle of Jena–Auerstedt in 1806.

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