Bandua was a theonym used to refer to a god or goddess worshipped in Iberia by Gallaeci and Lusitanians. Whether the name referred to a discrete deity or was an epithet applied to different deities is arguable.

The deity's name is found, in epigraphy, with a series of epithets:

In Rairiz de Veiga, Bandua is acknowledged as a god of the Vexillum and partner of Mars:

At Espinhosela, the name Bandua alone is found. At Codosedo, Alenquer and Xinzo de Limia however, the name Bandua is qualified by the epithet Aetobrico(m). At Cáceres, Bandua is qualified by Araugelensis, at Curbián by Bolleco(m), at Miguel o Anjo by Brico(m), at Mixo(m) by Calaigus, at La Mezquitilla by Itobrico(m), at Eiras by Lanobrica, at Rairiz de Veiga by Veigebreaeco(m), at Arcuelos by Verubrigo(m), at Seisco de Anciães by Vordeaeco(m) and at S. Martinho by Vorteaecio(m).

The theonym Bandua has been found recorded in Portugal and Galicia. Along with Cosus, Nabia and Reo, Bandua is one of the best documented deities in large areas of western and north-western Iberia: six epigraphies from the Province of Ourense.

It has been proposed that the worship of Bandua spread from the north (Gallaecia and Asturia) into the south (Lusitania), along with that of Cosus and Nabia, so contrasting with the worship of Reo that would have extended in the opposite direction.

According to scholars Jürgen Untermann and Blanca María Prósper, the form Bandue, and the form Bandua or Banduae, predominate in the Galician territory north of the Douro River, while the Bandi ~ Bande form is more common in the Lusitanian area to the south.

Professor Olivares Pedreño argues that, in relation to the attestation of epithets Roudeaco/Roudaecus, the name pertains to a place named uicus Rouda, and their discovery in different locations suggests a migration or population displacement.