Theudis was king of the Visigoths in Hispania from 531 to 548. He was the sword bearer of Theodoric the Great, who sent him to govern the Visigothic kingdom during the minority of Amalaric, the son of king Alaric II and Theodegotho, the daughter of king Theodoric.

According to Procopius, during his governorship Theudis had married a Spanish woman who "belonged to the house of one of the wealthy inhabitants of that land, and not only possessed great wealth but also a great estate in Spain." With this wealth he was able to muster a private army of two thousand men, effectively making him independent of Theodoric's authority. Theodoric did not take any action against Theudis. One reason was that doing so would give the Franks, who had killed the Visigothic king Alaric in the Battle of Vouillé an excuse to take to the field once again. Another was that Theudis was careful to obey the commands of his king, and never failed to send the annual tribute.

Following the death of Amalaric, last of the Balti dynasty, Theudis was elected king. Herwig Wolfram believes one factor that led to his selection was support of fellow Ostrogoths who had gone west with him. Peter Heather posits a second, noting that several of Theudis' Italian relatives -- Ildibad and Totila -- became kings of the Ostrogoths following the fall of the House of Theodoric in the Gothic Wars: "They probably represent, therefore, a particularly powerful non - royal clan."

In 541, Theudis had to confront the Franks under Chlothar I and Childebert I, who had penetrated as far as Zaragoza, which they besieged for forty - nine days, but according to Gregory of Tours the Franks lifted their siege when they learned the city was protected by the relics of Saint Vincent of Saragossa. The primary sources disagree over the outcome of this Frankish invasion: Isidore of Seville writes that the future king Theudigisel, who was then a general of Theudis, had killed all of the invaders except a group which had bribed him to allow them to escape; Although Gregory of Tours writes that "they succeeded in conquering a large part of Spain and they returned to Gaul with immense booty", Roger Collins observes that this was the first Visigothic victory over their Frankish rivals -- an achievement which undoubtedly added to Theudis' prestige.

Early in his reign Theudis (533) received a delegation from the Vandal king Gelimer seeking help against the impending Byzantine assault. Theudis received them cordially, throwing a banquet in their honor, at which he asked them how matters were at home. The envoys had travelled slowly to Hispania, and out of contact with events in Carthage; meanwhile a merchant ship, which had left Carthage the same day it fell to the Byzantines, encountered favorable winds and reached Hispania first with the news, which Theudis had known when the Vandal envoys arrived. So when they proposed an alliance against the Byzantines, Theuder declined, telling them to go to the sea coast, "For from there you will learn of the affairs at home with certainty." Puzzled at this response, the envoys eventually followed his advice and returned to Carthage where they were taken prisoner by the victorious Byzantines. Roger Collins suggests that Theudis exploited the Vandals defeat by occupying a portion of North Africa opposite Spain. This would explain why in 542 the Visigoths made an unsuccessful attempt to come to the defense of Ceuta, when the Byzantines besieged it from land and sea. According to Isidore of Seville, the invading army refused to fight on the Sabbath, and when the Byzantines learned of this attacked the Visigoths and left not one alive.

Despite his being an Arian Christian, Isidore of Seville praises Theudis, for he not only tolerated the practices of the native Roman Catholic citizens, but permitted their bishops to meet at Toledo to arrange "those matters which were necessary for the teaching of the Church." Collins notes that "of the few provincial councils that are known to have taken place in Spain before 589, nearly half were held during his [Theudis] reign: I Barcelonia in 540, Lerida in 546 and Valencia also in 546." During his reign a further codification of Gothic law was effected and promulgated November 546, quoting numerous Roman authorities.

In 548, he was assassinated in his palace by a man who had feigned madness in order to get close enough to strike the fatal blow. According to Isidore of Seville, as he bled out Theudis called out that no one kill his murderer, "saying that he had received a requital agreeing with his own deserts, because he himself too as a private citizen had killed his leader."