Charles III "the Simple" (September 17, 879 - October 7, 929) was a member of the Carolingian dynasty. He ruled as King of France from 898 to 922.

The posthumous son of King Louis II of France and Adelaide, Charles married Frederonne who died in 917 and he then married Eadgifu, the daughter of King Edward I of England, on October 7, 919.

As a child, Charles was prevented from succeeding to the throne at the time of the death in 884 of his half-brother Carloman or at the time Charles the Fat was deposed in 887 after he had succeeded Carloman. Instead, Odo, Count of Paris, succeeded Charles the Fat. Nonetheless, Charles became king at the death of Odo in 898.

The kingdom of Charles the Simple was almost identical with today's France, but he was obliged to concede what would become known as Normandy to the invading Norsemen.

In 922 some of the barons revolted and crowned Robert I, brother of Odo, king. In 923, at the battle of Soissons, King Robert was killed, but Charles was also defeated. Rudolph, Duke of Burgundy was elected king, and Charles III was imprisoned.

Charles III died on October 7, 929, in prison at Péronne , Somme, France and was buried there at the L'abbaye de St-Fursy. His son with Eadgifu would eventually be crowned King Louis IV of France.