Guillemundus (died 827) was count of Razès and Conflent, in what is now southern France.

He was son of Bera of Barcelona. He received these counties from delegation of his father (before 820) and retained them when Bera died in 820. In 826 he joined the revolt of Aysun

Aysun

Aysun was the son of Sulayman al-Arabi Aysun, together with his father Sulayman al-Arabi, joined Charlemagne's army that besieged Zaragoza in 788...

 or Aissó

Aissó

Ayxun ibn Sulayman ibn Yaqdhan al-Arabí better known as Ayxun or Aissó was an Islamic or a Goth nobleman who led a revolt in Barcelona, Ausona, and Girona in 826 to 827....

 and, routed, fled to Córdoba

Córdoba, Spain

-History:The first trace of human presence in the area are remains of a Neanderthal Man, dating to c. 32,000 BC. In the 8th century BC, during the ancient Tartessos period, a pre-urban settlement existed. The population gradually learned copper and silver metallurgy...

.

The name Guillemundus was given him in honour of his great father William

William of Gellone

Saint William of Gellone was the second Count of Toulouse from 790 until his replacement in 811. His Occitan name is Guilhem, and he is known in French as Guillaume d'Orange, Guillaume Fierabrace, and the Marquis au court nez.He is the hero of the Chanson de Guillaume, an early chanson de geste,...

 (Guillem) the Saint, count of Toulouse, cousin of Charlemagne

Charlemagne

Charlemagne was King of the Franks from 768 and Emperor of the Romans from 800 to his death in 814. He expanded the Frankish kingdom into an empire that incorporated much of Western and Central Europe. During his reign, he conquered Italy and was crowned by Pope Leo III on 25 December 800...

, but with the ending "undus" probably by the influence of William's wife Cunegunda.