Theoderic IV was King of Spain and titular Western Roman Emperor between 780 and 788. The brother and successor of King Athawulf, he was for years the leader of the anti-war party in Spain and as a result was elected king when Athawulf's warmongering resulted in defeat at the Battle of Myrtea. Among Theoderic's first actions were to agree peace and to withdraw from the conquered territories in Italy, Burgundy and Africa, before devoting his efforts to rebuilding the country.

This did not deter his other enemies, however, and he soon came under increasing pressure from the rising power of Charlemagne. Theoderic proved unable to resist the latter's predations, and when he died in 788 he had abandoned much of Aquitaine to plunder and ruin.

Theoderic was succeeded by his son, Theoderic V .

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