Louis the Stammerer (French: Louis le Bègue) (1 November 846 – 10 April 879) is the King of Aquitaine and later King of West Francia.

He is the eldest son of Charles the Bald and Ermentrude of Orléans.

He succeeds his younger brother in Aquitaine in 866 and his father in West Francia in 877, though he is never crowned Emperor.

In the French monarchial system, he is considered Louis II.