Viedma (Spanish pronunciation: [ˈbjeðma]) is a subglacial volcano whose existence is questionable.

The 1988 eruption deposited ash and pumice on the ice field and produced a mudflow that reached Viedma Lake.

[2] This volcanic zone consists of six volcanoes, from north to south Lautaro, Aguilera, Viedma, Reclus, Monte Burney and Fueguino.

[7] In 1956 Louis Lliboutry proposed that volcanic activity may occur in fissure vents buried beneath glaciers; between eruptions they would be concealed below the ice;[8] Lliboutry considered dark bands on the ice to be tephra deposits, a view supported by a 1958-1959 expedition that found pumice on the Viedma Glacier.

Most of the mountain is buried beneath the Viedma Glacier of the Southern Patagonian Ice Field and only parts of it crop out.

[13] A number of structures interpreted as craters and concave depressions are found especially on the southern part of the volcano, some of which are lined up in north–south direction.

Owing to their similar composition the three northerly volcanoes Lautaro, Viedma and Aguilera are grouped as the "northern Austral Volcanic Zone".

[18] Viedma like other volcanoes of the Austral Volcanic Zone has erupted andesite and dacite.

[8] A subglacial eruption occurred in 1988, depositing ash and pumice on the Viedma Glacier.

[2] The eruption had melted part of the ice and formed a network of valleys; it was assumed that it had taken place at some point between September and November of that year.