Louis III was King of West Francia from 879 until his death in 882. He succeeded his father Louis the Stammerer, and ruled over West Francia in tandem with his brother Carloman II. Louis controlled the northern part of West Francia (Neustria), including the capital of Paris, while Carloman controlled the southern portion (Aquitania). Louis ruled from March 880 to 5 August 882, when he died and left the rest of West Francia to his brother. His short reign was profoundly influenced by his military success, including his defeating Vikings in August 881.

In medieval historiography, West Francia or the Kingdom of the West Franks constitutes the initial stage of the Kingdom of France and extends from the year 843, from the Treaty of Verdun, to 987, the beginning of the Capetian dynasty. It was created from the division of the Carolingian Empire following the death of Louis the Pious, with its neighbor East Francia eventually evolving into the Kingdom of Germany.