Louis III (863/65 – 5 August 882) was King of West Francia from 879 until his death in 882. Despite questions of his legitimacy and challenges against his ascension to the monarchy, Louis would prove to be an effective leader during his reign, notable for the defeat of Viking invaders at the Battle of Saucourt-en-Vimeu in August 881 that would later be immortalized in the poem Ludwigslied. He also led a less successful military campaign against Boso of Provence with help from Charles the Fat.
The eldest son of Louis the Stammerer and Ansgarde of Burgundy, it was unclear during his early life if the young Louis had a claim on the throne of West Francia.