| Succession: | King of West Francia |
| Reign: | 877–879 |
| Coronation: | 8 October 877 in Compiègne |
| Cor-Type: | france |
| Predecessor: | Charles the Bald |
| Successor: | Louis III and Carloman II |
| Spouses: | Ansgarde of Burgundy Adelaide of Paris |
| Issue: | Louis III of France Carloman II Ermentrude of France Charles the Simple |
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| Dynasty: | Carolingian |
| Father: | Charles the Bald |
| Mother: | Ermentrude of Orléans |
| Birth Date: | 1 November 846 |
| Death Place: | Compiègne |
| Burial Place: | Saint-Corneille Abbey, Compiègne, France |
Louis II, known as Louis the Stammerer (French: Louis le Bègue; 1 November 846 – 10 April 879), was the king of Aquitaine and later the king of West Francia. He was the eldest son of Emperor Charles the Bald and Ermentrude of Orléans. Louis the Stammerer was physically weak and outlived his father by a year and a half.
Louis succeeded his younger brother Charles the Child as the ruler of Aquitaine in 866 and his father in West Francia in 877, but he was never crowned emperor. He was crowned king on 8 October 877 by Hincmar, archbishop of Reims, at Compiegne and was crowned a second time in August 878 by Pope John VIII at Troyes while the pope was attending a council there. The pope may have even offered him the imperial crown, but it was declined. Louis had relatively little impact on politics. He was described "a simple and sweet man, a lover of peace, justice, and religion". In 878, he gave the counties of Barcelona, Girona, and Besalú to Wilfred the Hairy. His final act was to march against the invading Vikings, but he fell ill and died on 10 April 879 at Compiègne, not long after beginning this final campaign. On his death, his realms were divided between his two sons, Carloman II and Louis III of France.
During the peace negotiations between his father and Erispoe, duke of Brittany, Louis was betrothed to a daughter of Erispoe in 856. The daughter's name is not known, nor is it known if this was the same daughter who later married Gurivant. The contract was broken in 857 after Erispoe's murder.
Louis was married twice. His first wife Ansgarde of Burgundy had two sons: Louis (born in 863) and Carloman (born in 866), both of whom became kings of West Francia, and three daughters: Hildegarde (born in 864), Gisela (865–884).
By his second wife, Adelaide of Paris,he had Princess Ermentrude (874–914) and a posthumous child, Charles the Simple who would become, long after his elder brothers' deaths, king of West Francia.
With his first wife, Ansgarde of Burgundy, Louis had the following children:
With his second wife, Adelaide of Paris, Louis had:
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