Louis Rudolph (German: Ludwig Rudolf; 22 July 1671 – 1 March 1735), a member of the House of Welf, was Duke of Brunswick-Lüneburg and ruling Prince of Wolfenbüttel from 1731 until his death. Since 1707, he ruled as an immediate Prince of Blankenburg.
Louis Rudolph was the maternal grandfather of Empress Maria Theresa, Emperor Peter II of Russia and Charles I, Duke of Brunswick-Wolfenbüttel.
Louis Rudolph was the youngest son of Duke Anthony Ulrich of Brunswick-Wolfenbüttel and his consort Princess Elisabeth Juliane of Schleswig-Holstein-Sonderburg-Norburg, daughter of Duke Frederick of Schleswig-Holstein-Sonderburg-Norburg. He became a major general in the service of the Habsburg emperor Leopold I in 1690 and was promptly captured in the Battle of Fleurus by the forces of King Louis XIV of France. After being released the same year, his father gave him the Brunswick County of Blankenburg as a present, with the consent of his eldest son Augustus William, insofar violating the primogeniture principle laid down by the late Duke Henry V.
When in 1707 Prince Anthony Ulrich managed to betroth Louis Rudolph's daughter Elisabeth Christine to the Habsburg archduke Charles VI, his elder brother Emperor Joseph I raised the County of Blankenburg to an immediate principality. Louis Rudolph's status as an Imperial prince (Reichsfürst), however, was limited as his vote in the Imperial Diet was not hereditary and depending on the Welf Electorate of Brunswick-Lüneburg (Calenberg line).
On the death of brother Augustus William in 1731, Louis Rudolph also inherited Wolfenbüttel, thus ruling both principalities in personal union. He relocated his residence to Wolfenbüttel, the capital of the inherited bigger principality. In the few years of his rule, Louis Rudolph managed to restore the finances, after Augustus William had almost ruined the state.
Louis Rudolph died without male issue in 1735. He was succeeded by his first cousin, Duke Ferdinand Albert II, who had married Louis Rudolph's youngest daughter, Antoinette Amalie.
Louis Rudolph married Christine Louise, daughter of Albert Ernest I, Prince of Öttingen-Öttingen, at Aurich in 1690. They had four daughters, but only three reached adulthood:
Many members of modern and contemporary European royalty are descendants of Louis Rudolph. In particular, with the exception of Albert II, Prince of Monaco, Louis Rudolph is an ancestor of all current sovereigns of hereditary European monarchies.