Rudolph Augustus (16 May 1627 – 26 January 1704), a member of the House of Welf, was Duke of Brunswick-Lüneburg and ruled as Prince of Brunswick-Wolfenbüttel from 1666 until his death.

He was born in Hitzacker, then the residence of his father Duke Augustus the Younger of Brunswick-Lüneburg and his second wife Princess Dorothea of Anhalt-Zerbst.

His father assumed the rule in the Principality of Brunswick-Wolfenbüttel, after his Welf cousin Duke Frederick Ulrich had died childless in 1634.

During his reign, Rudolph Augustus concentrated on the Baroque expansion of his ducal residence, including the Alter Weg ("Old Way"), a road connecting the cities of Brunswick and Wolfenbüttel.

They had three daughters: Upon the death of his first wife, Rudolph Augustus entered into a morganatic marriage with Rosine Elisabeth Menthe (1663–1701), which remained childless.